There's a thick film coating in inside of all my exhaust pipes, all the way out back. I was running very rich, unintentionally, because I was tuning the computer (stand alone). The A/F ratio is "normal" now, 12 at WOT. It was at 9~10 before. Anyway ff I run the car lean for awhile, just at idle, will the carbon burn off? Obviously I can clean it off by manually, but I'm lazy. What do you think?

 

No, don't think for a minute that your FD is a self cleaning oven. Get some carb cleaner and spray it in and that should get blown out when you start the car.