The Ferrari F355 has two different engine packages (OBDIO-I=95 and OBDIO-II=96-99), and three different brake packages (95, 96-97, and 98-99). In street braking, there is not much difference in the braking setup and response; and for track use all brake packages should have a set of pads that are more tollerent of heat.
When F1 became available in ?96 or 97? it arrived with an uprated slave cylinder in the clutch throwout system. Like the F348s the clutch (and associated parts) is easy to change even if the parts are expensive. If you have to change anything in the clutch, do the whole thing and use the uprated slave cylinder. Its smoother, lighter, and ever so slightly faster.
The 95 engine has a little more HP and TQ (5 HP and 2-3 lb-ft) from a slightly richer mixture allowed by the OBDIO-I emissions specification. All engines will have header issues if tracked regularly, and the 95 modle year is more affected than later. There is a uprated materials specification if/when header replacement is required. Even with the uprated materials, challenge cars replace the headers yearly. With indifferent street use headers have gone as far as 103,000 miles without failure. The hydraulic pump of the F1 cars saps some power from the engine but performance improves through the faster gear changes available through computer controlled timing of the events. The 360 F1 system is miles ahead in smoothness especially after 2001.
Engines up through the 98 model year can be affected by a valve guide issue detected in 95 based on the 94 348 Challenge cars where the factory changed the vavle guide specification from <some> bronze to sintered steel. In general, if the engine has not run into the valve guide issue by the time it has 20,000 miles it will likely not run into the issue.
The suspension system is excellent, with minor issues relating to the computer controlled shoch absorbers (connector corrosion). The oversteer/understeer relationship is easily manipulated with rear ride height (Google on: Ride couple distribution). The factory specs are just fine for street and even agressive track driving on street tires. I get 9 K miles on a set of max performance street tires where 1,500 of those miles occur on a race track with factory specs. Both front tires and both rear tires turn from treaded tires to slicks within 100 miles of each other. Adding camber speeds up the chassis but beware of making the car faster than the driver. Adding toe calms the car under steady state straight line operation and under braking. Running toe-out is only for track use. The suspension is easily dialed into the driver preference as long as the driver known which direction he want the cars response to move towards. If you lower the car be aware of a high speed heavy braking issue at the front suspension. Staying at the <already> factory ride heights (4.2" of ground clearance) is a good bet and prevents this high speed braking issue.
If you want to use r-compound tires or racing slicks, find the challenge specifications for alignment, but don't lower the car unless you also add the challenge spring and shock package. For noon-agressive track use, r-compounds and slicks work pretty well with the factory alignments.
The alignment system (shims) works so well that if you like agressive track driving and calm street driving, get the car sorted on the track first, and them get it aligned back to factory specs on an alignment gig. The difference between the shim thickness can be measured, and when you get to the trank, loosen a bolt, insert the required shims (8 times) and go to town. At the end of the day remove the shims, and presto you are back at street alignment. You will also get most of the toe change desired (out at track and in on the street) with this change as a side bonus.
I dislike the power assist for the steering and prefer the 348 feel of the steering wheel, but I rate this as a very minor issue.
Cars that are used hard over irregular surfaces will see minor paint spider webbing on the rear flying butress (C-piller) as evidence of hard use.
The plastic parts in the interior need to be kept away from Armoural and similar plastic protectants--it turns the plastic parts into a gooy mess.
The leather <especially> needs to be protected from drying out. Feeding the leather once every couple of months or every time you drive for any distance with the windows down; and avoiding letting the car sit in sunlight help a lot. The leather is higher in quality than <say> a C5 Vette, but less tollerant of lack of care.
Overall, the engine internals, the transmission, suspensions and brakes are basically unbreakable. There are no long term issues with the paint and exterior materials.
With the age of these cars approaching 10 years (95) and only the 98s and 99s still under the 8-year emissions warentee, the potential buyer is ever more dependent upon a high quality PPI than before. These are wonderful high performance machines that can take a lot of abuse (or designed for use) without fail. The engine has a big broad torque curve that is readily accessible and the sound at RedLine is simply out of this world. When the tail drifts out in a 100 MPH sweeper, you dial in a touch of steering and add throttle, and grin all the way to the next braking zone. However, like an Italian mistress, they are demanding upon your time and wallet. Choose wisely.
0) Get a HPi check , and make sure there is a history that makes sense. There are independent service places that are better than main Ferrari so a factory history isn't everything. My car hadn't been serviced for 4 years (but hadn't done any miles either) and I just got it back from belt/change major service and its fine.
1) Run your finger along all panel gaps to see if they are relatively equal and panels are mounted at the same level. There is usually some rust on the foot plates under the doors, its a pain to clean up as they are bonded and removing usually bends them. Can be replaced with carbon fibre panels (see eBay). There is usually cracks/ripples in the paint where the C pillar meets the rear wing. This is normal and is something that needs attention every now and again.
2) White powder in the tail pipes = new catalytic convertors. These are £400 each (x2) or can be replaced with pipes (£200 total) but they are loud and due to emissions require a friendly MOT chap. The standard cats do fail (ceramic). Fuchs in Germany will take your old Cat bodies and replace inner with metal matrix which lasts forever (£1000 I think - but one off payment). Note that if the Cats need replacing, either with other cats or pipes then each has 3 sensors (2 Oxygen and 1 temperature) and they sometimes cannot be removed so you need new ones (£160/£60/£100 each).
3) Interior black rubber dash covering cracks in centre console and breaks up. Starts on the ashtray - again carbon panels can be bought on eBay.
4) There should be NO oil leaks, no blobs under it at all. So dont accept the "Ferrari's always leak a little" argument.
5) When/if you check the engine oil level DO WITH THE ENGINE VERY HOT! ie not cold, if you check when cold (like I did) you could end up draining 14L out of the sump (holds 9.5) been there etc...
6) Rub your finger around the top of the dampers on the black rubber bushes, if there is any oil / damp then the damper is on its way. £600 each or about £200 as a recon from Bilstein. Also if rear dampers gone then you will see high wear on inside of rear tyres.
7) Gears selection should be heavy when oil cold (miss 2nd out to save the synchros) once hot the shift should be quick and smooth for all gears.
8) The paint should be even all over and a bit orange peally (normal Ferrari) if the paint finish is mega (no orange peel) then its either been professionally rubbed down and polished or its a re-spray. Look everywhere for overspray, lift the window rubbers etc.
9) Make sure wheels are not damaged, magnesium leaks air if it has hairline fractures and an impact can cause this. They are about £850 each to replace.
10) Exhaust manifolds crack and need welding / replacing at some point. Check for blowing in the exhaust system and adjust price as required. Ferrari manifolds are about £1650 each but there are alternatives that are probably better made (eBay again, .com, I love eBay ).
11) When you remove the petrol cap (make sure it dosnt stick when pressing button on dash, show lack of care) there should be a rush of air OUT (tank pressureised).
12) Check all the electrics work OK, and I mean all of them.
13) I have never seen a car with more than 30,000m on it that hasnt got signs of wear / cracking on the leather interior (seat sides etc) so if you see wear and the mileage is low be suspicious.
14) Throttle sticks a little bit on initial pickup (needs more pressure initially when pulling away then jolts as the pedal moves) this is caused by the throttle cable run not be properly adjusted/lubricated. Its a good indicator of how recently and how well its been serviced. After a service there should be no jolt, but it gets gradually worse the closer you get to the next service.