power loss

[HummerRidin26"kmc's]

I have a 2003 h2 its been a good truck i love the hell out the thing but out of no where while i was driving one day its started feeling really slugish so i changed the plugs an wires didnt fix, so i then had tranny flushed tansfercase fluid changed an front an rear dif. fluid changed just to make sure that they werent holding it back still no luck i have a dtc code reader no codes ever showed when i crankin it an take off it will be fine an twenty mins later i feel like iam drivin a school bus flooring it every where to get around twenty mins later it might be perfectly fine again ive been dealing wit this for months now changed o2 sensors new high flow cats still nothing. also the plugs that i changed looked orangish in color. one min it feel like it has 350 hp the next min it might feel like a 150 hp this is a major loss of power randomly thank you for you time an help