My 6.2 runs smoothly but hit the peddle and lots of black smoke - truck is sluggish and accelerates at a snail pace. I have put on a new air filter with some help but not enough. I have advanced the timeing with little effect. I was wondering if I turned down the fuel in the IP if this would solve the situation? I live at high altitude and do not have a turbo. Any help would be appreciated. This can't be normal.