My truck is putting out gray smoke, but not always. Sometimes it is good and black, then next time I start it up it is gray. Maybe some less power. Now is were it gets crazy. Just put in laser cut DV's from Scheid. Retourqued the studs, they were good. The valves were good also. Smokes more now, but gray and runs alot slower. I was getting 42#'s of boost now 32 and it doesn't rap up like it used to. I am going to replace the lift pump, reblead the lines, and clean the fuel heater. Any other ideas. It has been gray smokin for a while, but not always and the timing is dead on. What usually causes smoke like this? Air in line, lack of fuel, water in cylinder, or hopefully nothing expensive.