That would have been too easy! Can you keep a FP Guage on it or plumb one on the adjustable reg? Seemed like there was no rhyme or reason with my vst acted up, would either not start or when it did it would run really rich blow just about raw fuel out of the exhaust. Also had some wires that were shorted out running into the metal box,where the ecm is, the insulation was rubbed right off causing an intermittent no start at one time. Gl with finding the issue soon.

How old is your mechanical fuel pump?

Pull the mechanical fuel pump output line that goes into the VST. Place that line in a container and crank the motor over with the kill switch pulled and see how much fuel comes out of the mechanical pump. If you have lots of fuel the mechanical pump is likely ok. If not the mechanical pump might be your culprit.

The mechanical pump is about two years old and i upgraded the suction line to 1/2" about a year and half ago. I didn't have time to do your test this weekend. Hopefully i can this coming weekend. A couple weeks ago when it was a no start again the VST can was about 1/2 - 2/3 full of gas.