does anyone have a JDM header with the 2.5 inch collector bolted into an exhaust with 2.25 inch piping? i want to know what kinda of mods i will need to make this work. I was told possibly a jdm itr cat would solve my problems because it utilizes the bottle nose effect with a larger 2.5 inch end and a smaller 2.25 inch end. is this true? anyone have this set up? any comments welcome, thanks !

 

bottle nose effect lol

 

i'm in the same situation..i got a 94 gsr..soon to have a jdm 4-1 2.5" collector, and i have a 60mm(2.36inch) tanabe cat back. trying to figure out what to do since this header is longer than a gsr..thus i can't use my cat without cutting back my catback exhaust..and a 2.5 collector up to a 2.25 cat wouldn't be right..

 

get a cat that has a 2.5inch on one side and 2.25 on the other side.. they do build them like that ... good luck