I've got an OFV on order. I'm gonna give that a shot first and go from there. I was going to check the spring height in mine tonight and found that I couldn't remove it without taking the top 14MM plug out first....well when I took the top off, the *&%^ spring shot out and I haven't found it yet So just for kicks I took the ball bearing and spacers out and reinstalled the OFV. Amazingly the truck runs. It is slightly rough at idle but drove it around the block and seems to have good power although fuel PSI is about 5, so I parked it until OFV comes in. My wife is going out of town for the next few days to see her parents so I really had no business tinkering around, but that's just me....been doing it all my life, hard headed I guess

 

You need to take a grinder and relieve the head a small amount to allow the overflow valve to come out. I have a new one in the garage waiting to go in but I to need to grind the head also.

 

Many of the new style OF valves don't have the removable head and come out/in without hitting the manifold. Otherwise grind or file the notch on the manifold.
Don't make the mistake of bending the return line to remove the valve, it makes it very difficult to get it back in the right place.

 

Installed new OFV, pressure is at 28-30 PSI idling but pulls down to 20-22 PSI under hard load. Cruising at about 25 PSI. At what pressure does a lift pump need to be at to make truck run rough? I don't want to damage the p7100 if that's possible. I did notice that the truck seems to be quieter idling cold now.

 

I've always figured as long as you're above 20 psi you'll be ok.
My 3500 will pull down to 20 psi pulling 26k up a 6% but cruises at 30 psi with the same load on the flat.
You're also going to find that fuel pressure is affected by fuel temp. Pressure goes up in the cold and down in the hot.