ISX low power

I've got a 2006 379 with a isx 500. Problem is sluggish response and low power. A while back it was starting to feel real sluggish and have low power. I pulled the air inlet tract off and cleaned all the carbon out and cleaned the sensors. I also pressure tested the charge air cooler ( no leaks at all) ad pulled the turbo apart and inspected the vanes. Put everything back together and it ran superb, power and response was great, fuel mileage was up also.
About 3 weeks later it started to act up again. Same symptoms. So far every sensor has been replaced, turbo has been replaced, vane actuator has been replaced. Fuel pressure is rite at 300 psi. There almost seems to be a lack of fuel though. It will get to 40lbs of boost but it doesn't seem to be making power. Before when i used to accelerate it would puff out a little black smoke, now there's nothing, egt's will get very high also. I don't believe it's the egr valve due to the lack of smoke, and disabling it makes no difference.
Help!!! Any suggestions would be greatly appreciated.
Thanks in advance

 

I'll check the wiring harness I guess, definitely can't hurt. I have a set of metering actuators on a cm871 that I'm not running rite now, I can swap em to try if it will interchange.
Thanks fellas

 

I'll check. Thanks

 

I didn't have a set of actuators that would work, but I did put in a new fuel pressure and fuel temp sensor along with the two relief valves in the front of the module. Ran perfect, almost all day. On the last load manifold pressure dropped to 20lbs and got real lazy again. Got back to the shop, shut it down for an hour or so, and now it runs fine again. Any other suggestions? I'm ready to send it to the scrap heap.
thanks again for the help fellas