Intake, exhaust, no cat.
Bumper is a bit brown, would pulling the negative terminal on the battery help it?

 

You could try resetting the ECU (disconnecting - terminal) However it may only help for a short time. There is probably something mechanical causing the rich AFR that will cause the condition to keep coming back. When was the last time you did a full ignition tuneup?

If you pull your spark plugs what do they look like? White, tan, brown, Black, dry, wet ..etc..etc..

 

This is gonna sound bad, but never. So that WILL be on my to do list today. I'll pull the negative terminal, then wait, and maybe it'll help.

 

Letting it go for too long can also damage the O2 sensor(s) and pulling the battery may not help if it is already fouled. It will usually throw on the check engine light if a rich mixture is run for prolonged time. Hopefully when you do a tune up it will help. It should help with your MPG as well as clean up that bumper

 

This will sound strange. My F22B2 was running rich for tens of thousands of miles, between 330,000-350,000 I would say. It would shoot black out wot. The exhaust smelled awful, like nothing I've ever smelled come out of a car. It was like a wet burning leaves smell. It would fill the cab at a red light with window open. My oil would go black within 1000 miles. BUT the car was in perfect tune so I kept driving. Then my fuel pump dies and I change it and the car smells nice and clean. You could have a pump that is over fueling.