Alright, this is kind of complicated, so let me try to get it all straight... the car is a US 98 GS-R. My engine is a 95 JDM B18C1, I'm looking to redo the exhaust over to 2.5" over the 2.25" stock. I realize the header will bolt up, will an exhaust made for ITR's fit over the real trailing arms and fit in the underbody channel of my GS-R? I realize I'll have to get an ITR catalytic convertor as well... so will it fit into the underbody when everything is bolted up?

I've already done the search for this thread and couldn't find anything using all of the phrases I could think of. Sorry if this is a repeat post.

 

It should be the same bends with slightly bigger piping, that's it. Should fit.

 

Yes...as long as you go with all products to fit an ITR (header, cat, exhaust) it will fit!