after having a fast dohc neon, mazda prtoege5, and a blazer extreme i finally got a itr.......i have a aem cai and tein springs....i getting a dc jdm 4-1 header.....i see everbody saying they have a test pipe? what is this just? a pipe in place of the cat or what also i saw people saw to have a muffler shop make pipe and dont wast money on a cat back? i was thinking skunk2 catback? my buddy works at meineke muffler so i can get pipe for free but it isnt madrel bent.