yo im pickin up a jdm 4-1 header , i have a apex'i n1 cat back with a stock cat , am i gonna need to change anything to make this work? i think i remember it not fitting possibly . thanks

 

That JDM header won't fit up to the oem USDM cat.

You need a larger cat (I recommend the 2.5" carsound cat from IPS Racing or SMS). A larger exhaust to complement the larger header and cat will also be optimal for you.

 

jdm 4-1 header is longer than usdm itr header so you might need to get your piping redone or just run a custom "test pipe" *cough*straight pipe*cough* to make it fit properly, its not just a bolt on affair.

 

good question