I am helping a friend with his 6. 2, he knows even less about them than I do, and I don't know squat. I took off his air cleaner top and the area that would the clean side of the top is coated with black carbon. Anyone know why that is. It looks like the inside of a gasser tail pipe that is running rich. This truck is a 1985 GMC. I cannot find the fuel filter, where do they hide that, under the saddle tank shields? He also is having problems with over heating and low power, but I would guess that is because of no turbo and dragging around a big old glass boat up steep grades. I did tell to service the cooling system and get the auto fluid changed. Any help and ideas would be great, thanks.