i just went to autozone and they did not have the gasket i was looking for. The noise is very annoying, and i know its got to be something simple making the noise.....who would have thought modding a car would be so difficult

 

It turned out to be the 02 sensor that was loose in its bung, quick fix and no rattle, also way better sound now that its in!

 

Since we are on the topic of rattling. My T1R(re-uses cat heat shields) test pipe rattles/resonates at 3000-3500rpm. It rattles much more than a non shielded version I previously ran. I tightened the flange bolts and cat shield bolts but it still rattles. I'm thinking it might be the heat shields on the chassis