Had a P0303(Misfire Cyl.#3) code a few weeks back (CEL was flashing then went solid) Re-changed plugs(Autolite APP104) and wires(only 2 months old) still had misfire. Replaced both coil packs and had injector cleaning done, still had problem . Then I found a bad injector on cyl.#2,Replaced and truck ran better but not great. Pulled the # 2 plug and it had white ash on it(Guessing detonation?)Replaced plug and it ran great for 2 days then the miss came back. Now the # 1 injector went bad an this plug has the same white ash on it. Wouldn't run good until I replaced that plug. Now it's running great. I guess my ? is the lean mix causing this white ash.

 

You have something in the gas.
Drain tank, replace filter and refill with known good gas.
Ash as i know it does not come from running lean or rich. It's already something in the gas causing (deposits).
That's why you get temp correction until it happens again.

 

Just put on a new fuel filter and filled up with fresh gas.The forum won't let me post a picture.Put around 100 miles on it, so far so good.