I want to get a carsound high-flow cat. for my b16 w/ dc 4-1 usdm(2.0" collector), and apex N1(I think the piping is 2.25"), so would it be alright if i got a 2.25" cat., or do I have to match same diameter to my collector from header?(2.0")

Also: I measured the length from flange to flange of my stock cat, measuring 17", anyone back me up if this is precise?

 

i dont think u have to match it...im not an expert on high flow cats or anything...i got a high flow on my car with stock header...i guess as long as its not choking i.e. having a smaller cat or piping than u need than it should be fine

 

That's right, as long as it's not choking it's fine.

 

Bump. Does anyone know the exact length of stock b16 cat?