Hello, long time viewer first time poster. You guys have helped me already more than anyone knows. And that I appreciate. However, I'm tired of beating my head and searching relentlessly.

What I'm working on is my early 99 (build date 11/98) F250 2x4 7.3 6spd. The issue I'm having is serious intermittent power issues. Feels like I'm running on 4 cylinders. Little to no boost. Audible, but cannot feel any boost. I'm talking foot to the floor in second gear taking 20 seconds to hit 35. However, this issue isn't constant hence the intermittent part. Sometimes it'll run fantastic, other times it'll kick and buck for 30 minutes then smooth out again. Other times it'll run doggy for 2 days. Last week it was fine for 5 days in a row. Personal record!

Today I was on a straight stretch trying to make it home and it seem to have stalled. Got to the shoulder and truck idled to it's death. I'm new to diesels, so I drained the fuel bowl, primed it back up, and it started and ran like a new truck. Previous to dying, it was running like a salted slug for 35 minutes.

Parts I've replaced and verified bad were both UVCH gaskets, ICP had oil in the connector so it's been replaced as well. Torqued injector pedestal and hold down bolts as well I've also unplugged my EBVP, as well as pulled my vacuum line off of the wastegate diaphragm to rule out any wastegate issues. My boots are tight and rip free, cleaned those while I was doing my harnesses. I plan on doing oil, filter, and fuel filter tomorrow evening as another baseline.

The truck is throwing no codes. Scanner will not do function tests. CEL is functioning.

Any pointers, recommendations, or troubleshooting tips would greatly be appreciated. I have nearly every tool at my disposal. I have a very strong gas automotive background but I know nothing about diesels besides which pump to use.

Thank you in advance.