For a temporary test, try blocking the power piston into the lean(up) position. There's a few ways to accomplish that without doing any permanent modifications. If the plug fouling stops, then find the vacuum loss or other reason the plunger is staying down all the time. Plug fouling that bad can't be corrected with hotter plugs.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!