I have been fighting a similar problem, mine hesitates on take off and seems to mis under load at lower >1500 RPMS.
I have checked every thing but compresion and fuel injectors
most of my sensors have been replaced including: EGR, MAP, IAT, and some I can't think of right now. I checked all
Fuel pressure is good.
cats are reemed out and new muffler.
The schrader valve is an electrical switch inside the cab under the dash attached to the firewall to the left of the brake pedal.
I have been considering fuel injectors since I started but not sure how to check. You can check resistance of the selonoids, but if one is bad it should throw a code.
I have not checked mine recently I will need to clear them first and then drive around to generate new ones.