Engine protect syndrome?? HELP!!

[4x4horses]

My truck is a 2500HD SIERRA 2001 6.6L DURAMAX

I have a frequent problem that the engine goes into protect mode.
- 1900 rpm max
- Computer indication is massive fuel teak( Loss of fuel pressure )
Careful inspection reveals no fuel leaks. Including dealer testing.
Vehicle milage is 152,000- all eight injectors changed at 125,000.

Vehicle pulls well until computers indication of the problem.
When the problem occurs I am driving up hill 4-5% grade.
engine is usually 1800-2200 rpm.
This climb must be significant length 1/2 mile or more if unloaded.
If I am pulling the $ horses ~8K w/trailer it will cut out on the firast highway acceleration to 4th gear. Seems to wait until this point.

The fuel pressure sensor/computer has been changed and GMC service has spent 3 days looking for the problem.

The last service inspection diagnosis was that air was entering at the filter. The truck did the same thing again less than 1/2 mile after it was "fixed" and returned to me.

I note also that I some times loose all of the climate controls ( A/C heat Etc only the fan control works). When I turn the ignition off and restart the climate controls come back.

Is there a common electrical connector that could be loose?

Am I looking at a computer meltdown?

Does anyone have experience with this kind of trouble?