After my last run at VIR, my car sounded AWFUL at idle, and even worse after startup on a cool day. It sounded like I had valve or chain problems that would cost $$$$$$$ BUT, the car ran fine and sounded great at speed. This led me believe that it was probably a loose muffler. Kurt M. was kind enough to put my car up on his lift, and after banging around awhile we (being the royal we) determined that it was a bad cat. It didn't sound bad at speed because the exhaust pressure held the inner part still against the cat. Sure enough, that was the problem.
Deja Vu all over again. After my last run on the second day at Mid Ohio, my car sounded AWFUL at idle. Many there told me it was bad, but I recognized the sound. Sure enough, the OTHER cat failed. I just found out that the cats failed because my plugs were bad (at only 15k

) so fuel apparently was getting dumped into the cats where it was igniting and burning out the cores. Good news is that the problem will be fixed and the cats are covered under warranty (thank god). Bad news is that the plugs are not, but what can you expect.