Sounds like i m having the same type of problem. I have the IP replaced and fixed it for about a year and started again. So i dont think it was the IP. i wouldnt even say it fixed for a year.

yes and i replaced the lp which is the fuel pump on the frame rail correct?

No the pump on the frame rail is your LP (Lift Pump). The IP is the injector Pump on the top of your motor right in the middle of the valley between the heads. It is where your PMD is. This is all new to me but i have already replaced them so thats why i know where they are

ya i know thats what i said i have replaced the lp and pmd

1 thing you need to make shure that you have the highest cold cranking amp batteries
at least 750 or higher - this will make shure the pmd isn't damaged during cranking due
to low voltage - also you need to check your ground at the passenger rear of the cyclinder head they tend to vibrate & brake the wires or terminals - also add star washers to the connections to help get a better ground

I heard the very same thing from a guy, and his Oil Pressure Switch was the pronblem, his oil press. guage was working, and everything, but his test said his lift pump was bad, when he opened the copper petcock at the front top of the engine the one designed to drain off sediment and water separated by the fuel filter, if the engine stalls when you open this petcock, supposidly the lift pump is bad, and so he bought the lift pump and oil pressure switch, replaced the switch and the lift pump came to life and the problem went away, try it its cheap and makes since to me. good luck, ..Let me know if this works. please.

thanks for the info. I found the oil switch was the problem & now it runs like a champ