Intermittent smoking issue

[westernair]

Well I am having an intermittent problem with my truck wanting to smoke (dirty habit). For whatever reason I can be driving down the freeway and it decides to blow a bunch of smoke out the tail pipe. The engine still sounds the same, no change in performance and no increased head temps are seen. Seems to happen for no apparent reason and then as mysteriously as it started it goes away. Could this be a sticky valve, or what? Should I pull each of my heads and inspect them, run a cleaning agent though the oil for a few miles before changing the oil or???
Any help would be appreciated.