The screw in the side of the throttle body is the idle mixture screw. You shoul hand tighten it to bottom and then back it of 1 1/2 turns. When the engine is running it is adjusted for a smooth idle.
I don't know what you mean by gas sitiing on the "heads" but unused gas tends to leak out aroun the throttle pivot.
Now is the time to move the timing ever so slightly. I would try a very small clockwise rotation first. This would give less advance.
Good luck and please let us know how it goes.
