98 Jetta: Rattling/grinding sound

I have a grinding/rattling sound coming from my car when I hit bumps going pretty fast or going up a hill or got a alot of ppl/weight in the car, it also does it sometimes if I'm accelerating fast. I have brought it into 3 places to fix the prob... I've have the catalyst converter and the heat shield replaced. Any suggestions for what the problem could be or anything else that should be checked out to maybe determine where these lovely sounds are coming from?

Well is it coming from under the car, the wheels, or the engine. It might be the struts if it is coming from the inside a wheel well when you take turns, or hit bumps. But a little more info would help. See if you can determine the origin.

Sounds like the exhaust is hitting the body. Have they checked the exhaust hangers. Also, the motor mounts may be bad causing the engine to twist too much under acceleration causing the exhaust to hit.