it runs fine when its cold. loses power when it warms up.

[punkblackS14]

so ive searched and read and researched, and come up with squat. I love my car. its a phat car. its s14 240 for god sakes, but im losing faith in my car. when i start it up in the morning. (or afternoon or night) and the car is running cold, she runs like a horse in the wind. breaks loose like i want, shifts like i want, scoots like i want. Untill i get like a mile down the road and she warms up.... then all that power that i know she just had, is gone. the low end is the same, but from 3000-5500 it feels like somthing is bogging the motor down. could this be a timing issue?
(i know the timing is different during warm up) or an air fuel ratio issue? my mods are a stock air box with lower half removed and a k&n stock replacement filter. i have cleaned the MAF with carb cleaner, and the throttle body. i have no cat... on a stock exhaust.
(including pre muffler. could it be clogged?) any in put would be appreciated.