trucks been runnin like shit lately, took a fuel sample and gas is dark yellow and has an oily layer 2inches thick in bottom of 20oz pop bottle. anyclues on how to get rid of it?

Ahh drain the tank.

will the stuff stay on the sides and bottom?

I have no idea and couldn't even take a guess. Worst case pull the tank and flush it.

Take the tank out, drain it completely. Do not reuse the old gas. Clean it right out, also get a new fuel filter.