Could that be the muffler coming apart internally? I think there is some sound dampening material in our stock mufflers, probably in the resonator chamber and that might be what's on the ground covered in carbon. I've seen a guy locally have that happen on the dyno, but we knew the muffler was shot.

 

Wow, how did it drip out like that? I don't have a cat with 60# injectors and mine just builds carbon on the exhaust, I've prolly got a good 1/16th inch of build up on the tip alone!

 

my car ran really rich at high rpms on the dynojet. I had the old intense stage 3 (2.8 w/ maf-t) and injen cai. But it doesnt do what yours does at idle