does the jdm 4-1 headers need a modifed cat or a test to fit or will it bolt on cool with no problem?

 

i am pretty sure it replaces the cat. so if you wanted one it would prolly be modified.

 

It won't work with a standard cat... Most cats or testpipe have a 2.25" inlet, that will not work with the JDM ITR's 2.5" dump... I've seen testpipes with a 2.5" inlet that are made for the JDM ITR header... I'm pretty sure you'll still have to modify the length of the pipe... Good Luck

 

I see thanx for your help!! it turns out the one i bought last night has a 2.25 flange or collector welded onto it already!!!