Loud vibrating sound from centre/rear of car

[Razmataz]

Hi guys i just bought a 1995 325i convertible and its been running real good. Its recently started making a loud vibrating noise when i have people in the car. The sound only starts when i hit about 3000 revs plus and sounds as if the car is struggling to pull away. Just wanted to see if you guys can help before BMW take me for all i got!!

[LOS]

Check the catalyc converter by hitting it with your fist. If it rattles, that could be your problem.
How's the gas millage? Not too sure on your model but have your module scan for stored codes.

LOS

[thekid]

Only with people in the car? and when you say center rear you mean behind the center console and under (where a center rear passangers feet would be)?? Is there a bumping feeling with the noise? And does the noise increase with speed/rpm? And if so is it only speed or only rpm?