Fueling problem?

[TX Gooseneck]

This one has me lost.



I bypassed my TST box today with the supplied plug so I can send my box in for an update. The truck idled fine and was running fine under easy driving conditions. I put the truck in 2nd gear to leave from the light (after driving with a box for so long, driving without one sucks) and I floored the truck. At 3k it was like someone kinked the fuel hose. I shift to 3rd and it does it again, 4th, does it again. So I pulled onto the county rd I live off of to do some testing.

2nd - shuts off at 3k

3rd - shuts off at 2800 and 3000rpm

4th - shuts off at 2500, 2700, 2900, 3000, 3100, 3200, 3400, & 3500

5th - shuts off at 2400, 2800, 3000, 3200

6th - shuts off at 2800 (hit speed limiter before it did it again)



Climbing over 3k is a VERY slow. When I say shut off, the truck is still running but it honestly feels like some one is kinking a garden hose and the truck just rolls over then goes again to the next point of shutdown.



I'm not throwing any codes and my mileage has fallen off at a healthy clip (525-540/per fuel up now vs 650-725/fuel up a few weeks ago)



I have a rattle coming from what sounds like the right side of the engine under load, not sure if it is turbo related or not, but the impeller shaft seems to be tight or if it is something rubbing.



I am at 246,000 miles right. Stock fuel pump, converted to in-tank lift pump (approx 65k miles on the lift pump), fresh oil change, fresh fuel filter.



I'm not dumping fuel out of the blow by tube, so I don't think my injectors are dying.



I'm going to try to get it up on a lift tomorrow and see if it is anything simple, but any thoughts for this evening?

 

[TX Gooseneck]

Update: Truck goes into the shop on Mon. but I took my mechanic for a spin today and he thinks it may be the spring that allows the pressure relief valve on the fuel rail to blow off if pressure is exceeded. I get a bad injector rattle with the box on under WOT where the fuel is cutting off when the box is off. But you can see a power loss for sure vs. before (box on vs box on same settings)