1999 Chevy Suburban 99 Chevy Suburban no power

Ok my question is my truck seems to be losing power and has really bad gas milage. It doesnt buck or have a hard time starting nothing like that.I have checked the cats did the injector update, changed out the MAS airflow, coil, and map sensor. And still no diffrence the way it feels like from a dead stop it just dosnt wanna get up and go. Once it hits 3000 it feels like its not pulling anymore. There is no check engine nights on no history codes. Please help I was thinking of doing the fuel pump but the pressure is 55 at idle 60 on pedal. The only other thing I can think of is the o2 sensors. Any ideas thanks