6.9 loses power, gets it back, loses it again.

[ecvpaul]

I have an '86 Jayco motorhome on an E-350 chassis, with a 6.9 engine and ATS turbo. Coming home from a trip last week, I started to lose power on the Interstate, going from 55 to 45 to 40 (on a flat section.) I exited the freeway, and on the offramp I tried to rev the engine in neutral, and it felt very sluggish. It then stalled. When I started it up, though, it revved up fine and the power was back. So, I continued on down the road and it ran fine for about twenty miles, but then it started to lose power again. I had to stop three times, let the motorhome sit a few minutes, and then move on again. I figured my fuel filter was ready for a change, so I replaced it a couple days ago. I let a friend use the coach today, and he had the same problem. He noticed that when going up a hill, the egts were very low during the "power loss phase." I noticed this too on my trip (no higher than 600 degrees going up a hill). No smoke. My friend also heard what sounded like a vacuum leak from somewhere near the top of the engine around the fuel pump.
Any thoughts?
Thanks!
Paul

 

[sle2115]

Wouldn't be vacuum, these are open plenum engines, thus the need for a vacuum pump. I'm guessing fuel related, lift pump going south or gone and/or the IP may be in need of replacement. Being it's turbo, there could be an issue there with the turbo not spinning correctly, maybe not enough lubrication, etc.