Re: Weird Noise Under Drivers Seat
My cat died a week ago, and if you hold the rev's at about 1500, it rattles like crazy. does it thump when you back off the accelerator?
If so, then it could be loose engine mounts. This tilts the engine slightly which causes the exhaust to pull and knock the bottom of your car.
Get an exhaust specialist to look at your cat, or check the enginge mounts.