Help me with my Jetta

CTS

How do you know it's rich? Fault codes?

I BELIEVE it is running rich, my back bumper turns black, and my exhaust pipe is black and it tends to look like it puffs a blck "smoke" out the exhaust.

Normally there should be fault codes unless it's running not rich enough to set a fault. Might be a lazy O2 sensor. But start looking at other tail pipes for comparison. You maybe surprised what you see.

OK Where is my diagnostics center on my 94 jetta? I havent plugged it in for any codes yet.

remove ashtray in the front and then slide the DTC connection cover panel over into where the ashtray normally sits. You should see an engine on that panel that hides the connection.