random loss of power

[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

[Boss Hoss]

When I have bad gas, it really ruins my performance, perhaps teh same is happening to your truck?

[ROUSHDEMON]

might be bad gas, but I think he means that its happend for months.... change gas stations maybe? haha
I am NOT.... I repeat... NOOOOT a mechanic by any means, but I have learned a lot with my Roush, I've learned that on newer cars if the CPU detects that is getting really hot air through the intake it will sorta.... cut down your power by almost half as a "safe mode" so you dont blow the engine or damage anything else. I haven't had that problem with my Hummers but it did happen to me once with the Roush on the track 2 years ago when it was 106* degrees outside and I thought I blew the engine... well thank God I didn't, the car just felt like it went from 560Hp.... to like 89... ha! But I parked it under shadow for 30min, a fan and ice on the engine and its started right up with all the horsies back again....
Weird.... but I'd check your thermostat and that sort of thing.

... just a thought... good luck bro.