It sounds like you need to check a number of things!

I'll start with a few simple things.

If you haven't replaced both fuel filters in six months or so, do so! Add some boibore to your fuel (stops algae growth) Change air filter too! Make sure all six GP's glow. Ohms for each GP should be 03.0 to 08.0 but not 00.0.

Just curious, but does this engine still have the trap oxidizer?

Try this and report back.

BB