Mate, have you adjusted tappets before???... Not having a shot here in any way, just trying to get a grip on the situation in order to help you get this sorted.
Given what im reading here, If the Rig was running fine before you adjusted the tappets the only thing I can come up with is that somethings been done incorrectly.
The settings your using are correct at (0.38mm / 0.015 in warm) & yet its running like crap but improves after you opened up the clearance by .010, this sounds to me like its holding valves open.
My question is how are you determining your on the right stroke of the engine when you start the adjustment process???
Like I said, not having a shot only trying to help get you sorted.