I did some more testing tonight and I am really at a loss about this problem, and I don't want to end up in a financial loss... I banged on the exhaust system while it was hot (trust me it was hot). Nothing. So then I put a mechanics stethescope on the cat and then the middle (first) muffler and revved the engine (by pushing on the accellerator with a long stick). Nothing. I am not averse to removing the exhaust system for inspection but I am not sure what definitive test I could do. The only definitive test I can think of is to put on new exhaust components and see if the problem goes away. This is a very expensive way to test! Could it be the Cat even though it absolutely passes the "pound" test? Everything about it makes me think it is NOT pinging except the fact that the noise only occurs under some load and not with any amount of revving while standing still. I am really not sure how to proceed. I can go to the dealer and throw money at the problem and sort through all their lies and mistakes for the truth. Yes, I know I am bitter. I don't know any mechanic that I trust to figure this out. Am I "overthinking" the problem. The rattling is very loud and driving me crazy. Do I just bite the bullet and buy a new Cat on a whim? That would be at least $500 and if I do that and it still rattles, well you might read about me in the paper. Any thoughts appreciated.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra