Gunshot Pop From Exhaust&Black Smoke/Soot on rear bumper

[ayororo]

Hey guys, I gotta s13RedTop in an s14..

It seems its running rich kinda smells like a go-kart,

theres some blacksoot on bumper near muffler, and muffler turning blackish..

When I start pulling&Boosting Blacksmoke comes out of mufler I can kind of see it behind me..

and when im decelerating in gear while the rpms drop it makes the infamous GUNSHOT POP and I see some blacksmoke behind me.

Ive searched google etc but all of them had more symptoms I dont have,

The car honestly runs great&pulls hard So I dont thing theres piston/ring damage or im riding on 1 Less cylinder, boosts to 0.4 Bar, I have stock Side mount

I have stock SR with only CatBack Blitz Exhaust So I still have a CAT.