I'm planning on putting a new exhaust on my 98 gsr I think i have figured out the header and cat back exhaust

this is the header http://www.inlinefour.com/dcsporjdm41h.html

this is the exhaust http://www.typeoneracing.com/catalog...&cat=75&page=1

now i don't know about the cat these are both 2.5" and i believe the stock cat is 2.25" correct me if I am wrong what is my best option the get these to fit my gsr i am also open to different suggestions for the header and exhaust as I am not set on these for sure

 

Stock sized cat is smaller than that. You need a correctly sized cat for those pipes. Get one or a test pipe with the right size. If you get parts to match your oem size dont even bother.

 

Stock GSR?
Header I would go with a PLM Toda Rep.
CAT would be some kind of 2.5" (I've found this to be a big contributor towards RASP, removing it gets you the most rasp possible)
That T1R exhaust is nice but a bit expensive IMO.