Pix added.

 

Hopefully you find a solution because my truck does the exact same thing.

 

That's a recall replacement pump, it may have been timed right or it may not. Mark it and bump it 1/8" and see what happens.

 

Dave - thanks for the explanation on the pump. I decided to hold off on the timing bump, and see if taking out the fuel shutdown plunger would indeed fix my loss of power with that little spring getting weak, and boy did it make a difference.

I did not get to get it on the pavement last night, as I live down about 7 miles of dirt road, but my truck would get plum sideways crazy going through the gears last night, something it has not done in years. I had went ahead and bought a new plunger and spring at a local Bosch shop yesterday, so I am thinking that's been the cause of my crazy fuel pressure bounce and loss of power. I am not sure how that little plunger causing intermitten fuel pressure to the injectors could jack with fuel milage, but either way it would seem a 20 dollar part fixed my loss of power.

I had turned my pump down about a turn 6 months ago to try and conserve fuel, so I am looking forward to tweaking the pump again this week! Thanks to everyone who posted.

 

I had a feeling it was the the cutoff solenoid!
Glad you are back in business.