Troutstrannysvc

I noticed some white/grayish haze while under load on my truck.
I changed fuel filter, oil filter, oil, and cleaned the K&N.
Afterwords I only got to drive it only about 200-300 mi. and it was throwing coal black.
I was in an accident as of 11-19 and the truck sat for about a month, or a little less. And once I got it back on the road it was throwing coal black smoke still but then my thermostat was stuck open.
So I changed the thermostat, noticed it was leaking around the housing, flushed the rad/engine out put all new antifreeze in it.
Haven't noticed any antifreeze loss, or leaks, or drop of level.
But once in awhile it will start throwing white/grayish smoke, then after awhile it will clear itself back up throwing coal black?
I am not sure what the culprit is for this but I am hoping not a head-gasket issue.
As I said, I haven't lost any coolant, just replaced fuel filter not to long ago.

I was reading about the over-flow valve and I was thinking about replacing it, the fuel filter, and cleaning the pre-filter
When I get to the KDP next weekend I plan on checking the timing.
Does anyone else have any input?