Reduced engine power help

[Blue6.0HD]

Okay so i have an 04 2500HD with the lq4. ive replaced the TPS, the pedal sensor, and even the knock sensors. while i had the motor apart or while reassembly somethimg mustve gone wrong because after reduced engine power i have a very rough idle almost like it jumped time. however after you cycle the key and get it started again it runs fine. but often with little to no power. i have somewhere around 457k miles on the motor and it hasnt done this before. i know my fuel pressure regulator is bad and i have one ordered and on its way for me to fix which i believe solves my power issue, but not the reduced engine power problem. ive read that cleaning the grounds is an option and something about intake gasket failure could be a culprit for both. im going to clean the grounds and change the fuel pump assembly and see where im at but if that fails what should i look into? any info is appreciated

 

thanks