[Seawolf]

Mine started developing a weird almost harmonic buzzing sound in all gears when at about 1,800 RPM after about 6 to 8 months after buying it in July 2009. The dealer replaced the entire exhaust from the CAT back. Now, about 6 months after they replaced (I had gone a long while hoping it would get better) it is kind of doing it again, but this time on start up. You know how the engine revs a bit when you first start it? At the highest RPM mark during that sequence I can hear that buzzing again. But I can't replicate while driving. And since the car's RPM needle does a sweep at start up I can't even tell what RPM it's making the sound at this time.

On a side note, my car has also developed a "rattling" sound when going over rough or uneven pavement. The sound seems to be coming from the left rear muffler. I recently returned from a driving trip that involved some "spirited" driving; so I wasn't sure if I broke something or what.

I don't know if either one of these issues are similar to yours or not. I know it doesn't help your situation, but it kind of backs up your complaint with yet another experience. Hope you get it fixed/replaced.