I've had a problem in my 94 Z28 A4, and after using the search, I came up with this link:
http://web.camaross.com/forums/showt...ghlight=rattle

Exact same symptoms, 99% positive it's the same problem.

Now, I'm not familiar with torque converters at all. What stall speed should I go with for optimum performance? The car is mostly stock now w/ 90k miles, and when Im done will only be pushing around 420 hp (w/ 75-100 nitrous shot).
What converter should I go with?