Extra Soot?

I know that the 1GR's run a little rich and I'm used to seeing some carbon sticking near the tip of the exhaust, but recently my truck has been throwing so much that it is splattering all over the mud flaps and side of my truck. I've also noticed a rather sharp decrease in fuel economy (2 - 3 mpg). No codes are showing on the scanner. Any chance my O2 sensors are on their way out but haven't thrown a code yet?

 

I'd run a tank of Lucas fuel system cleaner through it then change the oil. A few squirts of MAF cleaner wouldn't hurt, either.

 

a/f sensor going bad can do this

 

I did the MAF and throttle body cleaning about a year ago and everything was pretty clean. I occasionally run a bottle of Techron through the tank, but I'm still pretty sure most "fuel system additives" are snake oil.

 

If you don't run a fuel system cleaner occasionally, olefin builds up in the injectors and can make them stick open (or closed) so I've heard.

 

Nope. This hasn't been an issue in many years.