im making my own downpipe and i have all this 2 inch stainless and i was gonna run 2 inch to my cat. i have the flange and all and i was wondering if it was gonna be too much back pressure. im going 2 inch off the turbo to 2.5 stock piping? what ya think

 

more info please. what turbo and what are your hp goals. IMO 2" is way too small for an FI application. but i guess if your only running 200whp on a d-series or something it may be ok. even NA catbacks are bigger than 2"

 

2" gonna restrict a non-turbo motor much less a boosted one.