All of a sudden, i have no power and truck sounds like a train - chug chug. Bad miss and no power some white smoke as well. I cheched the timing which looks great, but not sure if i should be looking in the distributer/wires/pulgs area (changed coil/rotor/wires/plugs 6 months ago)or if it could be a valve problem or what? 86 Blazer stock 305 with QJet. Was running great, and just started missing. please help! Thanks in advance!