SloCivicHMM

I just installed a comptech 4-2-1 header on my DOHC ZC (used the SOHC header) I'm guessing its the 2.25in collector correct, well I'm also running an apex N1 catback for my EG, 60mm I'm guessing........what test pipe would I run, I'm guessing a 2.25in pipe on both ends correct??? just wanted to make sure.....

SpoonEK2

Measure the collector first. Also, the N1 has a bottleneck at the cat/b-pipe flange which narrows down to 2". Cut that off and get a new 2.25in flange welded on. Then get a 2.25in carsound cat.

Being a gross polluter is not cool...