Truck Repair: turbo boast drops then unresponsive to load or throttle position, dodge dealer, boost gauge

Question
The fuel pressure is good but then again the problem is intermitant.  I get no indication the injector pump is bad ie easy starts plenty of power.  Is there is sensor that controls the boost?  I have a boost gauge and it is the boost that drops off.
-------------------------

Followup To

Question -
I have a 1999 ram 2500 with cummings diesel  
while at hwy speeds the boast presure drops to 6lbs and the truck continues to run but with little to no throttle response.  It will continue to do this until I stop. let it rest for a few minutes and then restart it.  It will then run fine until it it fails again this next time can be a few minutes latter to several hundred miles down the road and with or without a tow.  I had the truck at a dodge dealer in georgia for a week but he said he could not find anything wrong with the truck.  Can you tell me what might be wrong The truck has 150,000 miles and otherwise runs great

Answer -
First thing I would check fuel pressure to the VP44 fuel pmum.Should be no lower than 5 PSI with your foot to the floor.Then if that is low,change the electric transfer pump.I would get one from Cummins dealer they are around $150 but call Dodge for the bad price.The VP44 is around $1200-$1500.Change the electric pump if it is bad first & try it before the VP44.

Answer
Could be a sensor reading out of range & derating the engine.Like boost sensor showing more boost than actually have & derates engine until a good reading is acheived.Probably a laptop & a road trip are going to have to happen.I know Cummins diagnostic program will log all ECM data & then when you get finished with road trip just look to see what prameter is wrong.