Ok, run about 15 gallons through the fuel lines into another fuel tank, cleaned it all up, blew air through the vent line for about 5 minutes, changed the fuel filter, and replaced the coil. Good news no vacuum in the tank. Truck ran great, drove it for over an hour, worked it hard, not a single problem until BOOM, backfired, now it wants to backfire through the exhaust. Any ideas? Timing? Air-fuel mixture? Anybody know how many turns out on the mixture settings. Turning them does not seem to make much difference until you shut them both all the way down. Thank you all for all your help you are a great bunch. Hopefully I can pass on what I have learned to someone else that needs help someday.