ok, im buying a JDM 98 spec ITR header. I drive a 99 gsr. The guy im getting it from is also giving me a test pipe with a 2.5 inch collector at the tip that mushrooms out. Will have to do any other modification so that it will bolt up to my gsr? Some peeps say im gonna need a high flow cat. Please help

 

If you have a straight pipe already, you won't need a high flow cat. You can only use one or the other unless you want to be stooopid.

 

im not running a straight pipe though. i just need to know if i bolts up.

 

most likely need to hack the b-pipe

 

Never mind, I'm an idiot...

You will probably need a custom cat or test pipe built to mate the 2.5" collector to the GS-R b-pipe.