Stalling

[MrBouncer]

86 CUCV "stock" with the exception of doghead starter relay mod and GP controller card bypass, has ran fine for years but here lately has been stalling, only when cold and only after a sudden rpm change. Such as when fast idle kicks off, quick mash of fuel pedal and when stopping. And only cold. Replaced fuel filter, checked for leaks, checked IP return valve(glass ball). I am hoping cold advance but I am thinking the beginning of IP failure. Can find a lot of threads with similar problems but what I have found they get worse when the trucks warms up. SO any suggestions or ideas. Thanks in advance

 

[U1100L]

Lift Pump. If you can get a Vacuum / pressure gauge between the filter and I.P. that would help. I.P's like to be supplied with fuel 5-9 p.s.i keeps them happy. To much pressure will advance the timing.

F.Y.I Had 2 mechanical pumps fail, Switched to electric and got 6 months out of that one. You can hear it in the engine when they start to fail. like a change in tone.