If plugs have become coked up, started missing then became wet they never will recover.
I found with the std ecu on mine(L6) even when "set up" it was way richer than it needed to be, and this affected idling from cold especially, ie it didn't like it too much.
I would make sure everything is as it should be and check the phase alignment esp, if even one tooth out it will over fuel like there's no tomorrow.
That apart don't let it idle when not needed until at least the CO has been checked, or give a it a big foot every so often.
tabetha