4.3 idle issue

[1fstgto]

OK I’m pretty stuck on this one. My buddies 2002 GMC truck with a 4.3 vortec was giving problems where it would stall and run bad. Logged it for a quick drive and the fuel trims were very lean 18-20% at part throttle but ok at idle. Fuel pressure was under specs so a new pump and filter was installed and the regulator is working. Because of the mileage of the truck we decided to go ahead and do a few other maintenance items. The distributor cap contacts were worn and so we also put new cap, rotor, and a coil since it we were there anyway. Plugs and wires too. The truck ran great for days and the stalling started again. We noticed on forums crank and cam sensors were common topics so we put them in. Did a case learn and the next day it started again. Through all this the fuel trims got better but still out of range of my opinion of accurate. Today I had the thought that maybe it was the egr vale acting up so I pulled the egr valve to make sure the valve was not stuck open by carbon. Then we turned off the egr settings and tuned the truck. LTFT’s are with in 1 percent. And it feels better. Idle is still giving a problem. We tuned the idle and played around with the stall saver settings and raised the idle slightly. As far as I can see the milliseconds of the injectors increase for no reason adding fuel and causing the idle to drop while there is no change in STFT, MAP, or Timing. What I thought was weird that when this happens the injector duty cycle lowers. When this happens now after being tuned it catches itself where as before it would stall. We can not make it happen and now after tuning the truck it happens not very often. We actually had it idling for about 15 minutes in the driveway before it happened twice then it went away. And when it drops it will drop to almost stalling range.

Thanks in advance