I have a 88 silverado and the oil seals.egr.plugs have all been replace.the throttle has been replaced intake has been taken off twice and redone.i have no oil in the water or any water in the oil.the head gasket good i have compression on 6 cyl at 150 and 2 cyl had 125. The white smoke really starts coming out pipe once its starts getting hot.can anyone tell me what is it