I guess I jumped before I searched hard enough. I ordered a jic y-pipe to mate to my stock exhaust but now I'm reading that the oem mid-pipe is 2.5in while the jic outlet will be 3in. Question is so basically without chaning the midpipe I"m going to negate the effects of a free flowing y-pipe? Also due to the mismatch will I be causing an exhaust leak or damage to my exhaust/engine from extra pressure/force to overcome the mismatch? I've also found a couple posts of people getting rasp from the mismatch. Anyone who ran a stock exhaust with upgraded y-pipe have any comments?

 

from what i gathered in my350z.com, using an aftermarket y-pipe with the stock mid/muffler is bad