aaammmggg

I use a R320 CDi 224bhp car as my daily job as its a good motor as i find the normal mpv stuff crap. want more oomph from it and am unsure which way to turn. like the idea of the tuning box as i can turn it off if i get a problem what happens if i get a problem with a remap would like to know what people think about both the tuning boxes and also remaps

My play car is an hawkeye impreza but for work and daily stuff i have just got a 2007 R320 Merc. Not really bothered about manufacturers warranty and want to give it more ooomph, its not bad now at 224bhp but more is nicer. like the idea of tuning box so if i have a problem unplug it and car is standard. what happens if i get it mapped and have a problem id be buggered, could get recovered etc but would cost a fortune to get sorted so give a newbie some independent advice what shall i do?