i have a 2000 gs-R. at about 4k RPM there is a horrible rattle....sounds like a tin can. what might be causing this. it sounds like it comes from the rear passenger area, and will only do it when the car is in motion.
At first I thought it was the cat heat shield on my car, but I took it off and it is still there. I figured it was the A pipe, and the Acura dealer confirmed what I though, but they wanted $800 to replace it even though it is still under warranty! I guess I will just wait until I get a header. Check your heat shields though, they can cause buzzing around 4,000rpm as well.