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I think there are 2 possibilities here.
1- Your MAP sensor is failing and giving the PCM an erroneous pressure signal. If the sensor is showing a massive drop in manifold pressure, I'm guessing the PCM would probably back off on fuel since MAP is representative of the amount of air entering the engine.
2- The MAP sensor is fine and you are losing boost. Loss of boost could be due to a blown intake boot, loss of exhaust pressure from the wastegate opening, or some type of mechanical failure within the turbo. The pressures you are seeing are nowhere near high enough to cause the wastegate to open, but I suppose a failed wastegate actuator could be a possibility.

An independent boost gage will tell you what is really happening with boost and could help point you in the right direction.
 

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I fuel pressure gauge would be a good idea too.
 

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Good idea for the fuel pressure gauge. If fuel pressure is getting low enough to cause the engine to stumble, I would think that would cause a rapid loss of boost since you would lose exhaust pressure when you lose fuel.
 

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Discussion Starter · #24 ·
Thanks for the advice. I ordered a new MAP sensor--be good to have a spare if the old one is still good.
 

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Discussion Starter · #25 ·
Put a new MAP sensor in and cleaned out the sensor and tube (it wasn't clogged but had soot in it). I still have the same problem.
 

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I would invest in a Scangauge 2 or forscan to monitor some parameters when driving. You won't be able to see fuel pressure without installing a gauge and sender. I still think you are losing either boost by a leak or have low fuel pressure that you only notice when you are working the truck hard. Check for boost leaks to rule that out. A monitor would also tell you if you are losing boost.
 

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Sorry I read back. You already have AE so you are good. I still am leaning towards a fuel starvation issue. Have you rebuilt the fuel bowl pressure regulator ever? How about putting a new fuel pump on to rule that out? Even if it doesn't work I like having a spare on hand. Gauge is the best idea.
 

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Discussion Starter · #28 ·
I think I rebuilt that years ago. I'll monitor the fuel pressure today.
 
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