I've been reading up on why my exhaust rattles between 2800 and 3200rpms, but I've yet to find a solution. The car is a 98 DX originally from San Francisco. I 'replaced' my bad cat with some generic Ebay headers about 2 years ago, and ever since then it's had this issue. I replaced the muffler with an OEM one at the same time.

I've checked the heat shield (only one I have is through the little S-bend the exhaust does) and I don't think that's the issue. I also checked the hangers and bolts and everything seems pretty solid. I know the emissions laws in California are much different than here in Cincinnati, though I'm not sure that really matters. Also, not entirely sure the exhaust was stock when I bought it, so I'm not entirely 100% sure what's under the car. Right before the bend in the exhaust is a piece that looks to be a resonator, but I thought at one point I had read that California Civics had a second cat? Can't remember.

Anywho, the noise sounds to me like its coming from somewhere between the back and center of the car. The heat shield over the bend is slightly behind the driver, so that was the first thing I checked. I'd like to remove it, but the bolts are rusted on there real tight so that turned out to be extremely difficult.

The other odd thing about this issue is that the car only does it in gear. If it's in neutral I can rev it all day with no noise whatsoever. As soon as I put it on the road though, it's like clockwork. Starts right about 2800 and stops around 3200. It's definitely coming from somewhere behind the driver, but there's really not all that much back there so I need some help. I also thought this should rule out exhaust components but I wasn't sure.

This video is a decent idea of what it sounds like. Mine sounds slightly higher pitched than the video, but it's pretty close. The comments of the video are also interesting. Any merit to the idea of the pressure from the headers not playing well with the OEM exhaust? I've read lots of "EKs have that sound with no cat" posts, but I haven't seen anyone offer any solutions.

Any suggestions or comments are appreciated. Thanks in advance!