Turbo performance question

My brother-in-law and I, did a tune up on his 96 gst this weekend when we jacked it up we noticed he had no catalytic converter (he just purchased the car couple of months ago) we also noticed that the exhaust pipe started out about 3in. then about half way to the pipe it looks like they welded a 2in pipe to finish it off, not knowing much about cars we decided to call dealer who sold him the car when we asked him why did the exhaust had been modified he said it was better for the turbo because downsizing from 3in to 2in allowed more pressure back to the turbo IS THIS TRUE?? (how it past smoged I don't know incase you guys ask)

lower back pressure = better top end. more backpressure = better low end, to a point, if you weld the exhaust shut it wont give you any torque lol. backpressure is determined by the size of the exhaust pipe, the type of muffler, and the cat or lack of. do a search for "95_gsx_racer exhaust size" kevins done a couple write ups on the benefits of diiferent sizes. it may be in the write up section of the faqs too

To give the short answer, the dealer is full of shit. THe turbo provides more than enough "backpressure," in fact too much (the reason we all switch to bigger hotsides eventually). But in summary, velocity is good, backpressure is ALWAYS bad. ;)