Well it's an IDI engine alright, just not the IHC one we typically talk about here 🤣 Same principle of operation tho, so basic rules should still apply.

Anyway, grey smoke. Light but visible hazing when cold, mostly goes away as the engine warms up. If I push on the throttle about halfway down (such as when accelerating to merge on the interstate) it smokes visibly even with everything at normal operating temperatures.

Truck burns practically zero oil, so it's all fuel that makes the smoke. Fuel economy ain't terrible tho, but can always be better. Power is acceptable, but again more can be had for sure.

I'm thinking timing is off. But for the life of me I can't recall if grey smoke means timing is too advanced or too retarded.

Also let's say it's currently retarded and needs advancing or it's too far advanced and needs retarding - how does going in either ddirection affect heat generation inside cylinders? Head gasket being a known failure point, I'd like to avoid running the pump in a position where the timing causes much increased cylinder temperatures.