I have a DC ITR 4-1 header on my '99 GSR and a Type-1R 2.5" exhaust. The CAT has been replaced with a separate T1R resonated straight pipe. A couple of years ago my county started emissions inspection and I have not been able to pass inspection due to the check engine light and the fact I don't have a catalytic converter. I guess I am looking for a good CAT to install so I can pass emissions. I can probably work around the CEL, but the absense of a CAT alone is cause for inspection failure. What is the best aftermarket performance CAT I can get that will definitely clear the CEL and will be reliable? I looked for a DIY in the stickies but couldnt' find one. The car only has about 22whp more than stock, so I don't think it would be hard on the CAT.

It's been a while, but I think one of the O2 sensors right now is connected to the DC ITR header. I have the other O2 sensor in the house somewhere. So I guess I need a CAT that would come with 1 O2 connection/bung, right? And it should be a CAT that fits an ITR, no? Anyone know the length CAT I need? I believe the GSR and ITR CAT vary in length by 3" or 4". Or should I measure the straight pipe and that would be the length of the CAT I need? Can you please point me to someone who sells these CAT's or someone who is using one on a GSR with no CEL's?

Thanks! I need to get my beloved GSR back on the road!
Harry

 

You could weld the heat shield to the straight pipe to make it look like it is the stock one if it is simply a sight check tee hee or you could buy a magnaflow cat or other high flow cat and have it welded on. It will have very little power loss and wont have a CEL.