dave, try getting some wd40 and spray alot inside the exhaust, through the inlet and outlet, and the pressure fitting in the top of the pipe. kinda shake it around to break up all the residue inside.
you could have old gummed up fuel inside it blocking the return line keeping it from supplying good enough pressure to the tank. also, check and make sure your fuel tank is sealed tight. if you left fuel in it for a long time, it might have degraded the o-ring that seals the tank. I have noticed that with some of the HPI tanks, they have a problem with air leaks through the cap.
Might try a new glow plug too.