General Maintenance & Repairs - exhaust smell 98 Z28

So my friend was driving behind me today and said that when I got on the gas the exhaust smelled very similar to gun powder... What could be causing this?

My best guess is that the exhaust sytem has carbon build up in the muffler and is being forced out when I floor it. It is an aftermarket exhaust. No idea what brand but I'm guessing an old borla system. has quad rear tips that have a rolled lip. The ouside tips are tucked under the bumper more.

Mmmm, I love the smell of gun powder. :D

do you have cats?

It happens. Even with cats.

Guessing the cats are burning. Had the same smell from mine. Gutted them and no more smell.

Yes I have cats. Its a stock system with a magnaflow cat back. I'll be replacing the whole system eventually just wondering what it was. SLP 1 3/4 headers catted y pipe with SLP Loudmouth dual/dual.