HELP! Ecotec problem

Ok heres the deal. Recently my 02 auto ecotec started acting up. At WOT from 4 grand to redline it starts losing power. It kinda feels like the reduced power you get when u put the air conditioner on, like theres increased drag on the engine. The weird part is that this only happens about 50% of the time. The other times theres full power from the moment i floor it with no hesitation. It seems to act up when its hotter outside for some reason. Somebody suggested that my cat could be getting clogged but I only have 29000 miles on the car. I replaced my fuel filter and spark plugs and I still have the same problem. If anybody can point me in the right direction about what the problem could be it would be greatly appreciated.

Later
Chad

^

well seeing as you should still be under warrenty, take it to the dealer.

i have an 03 ecotec cavy, but i have no idea where my freakin spark plugs are!