Hey I just bought a downpipe for my 95 gst off a nonreputable site... They promised a "Full 3" pipe", but when it arrived the inlet was 2.5". I was kind of pissed but then I decided to ask you guys what you thought. First, will this be a big hinderance in the performance? and Second, does the inlet have to be 2.5" on a gst. I looked around and couldnt find one with the full 3"...just on the gsx models. By the way it was a Tsudo ETS pipe. Thanks

Very reputable companies do a 2.5 piping before the flex, and it works fine. When the exhaust is the hottest, it's compressed enough that it flows well through 2.5. I wouldn't worry about it at all.

another reason is that the o2 housing is 2.5'' where it connects to the DP. it is 3" after the flex section. if you look in the link in my sig you will be able to see the pic of the DP [scroll down] under the car and you can see the upper section is smaller than the lower section [after the flex]