black residue?

whats up, recently i've noticed a black residue/soot? around my tailpipe. I was wondering what would cause this to happen. Could it be that the engine running rich, or possibly the cat falling apart?

thanks.

i'm guessing that its just carbon deposits or its runnig rich

Have you jacked around with the fuel pressure? When my pressure was boosted I was getting mad carbons! Bumped it down a little now its better. So, yes, you are probably running rich.

It's just carbon deposits, you'll notice it on almost any car, just wipe it off