tecate4 vs kx 250

[tecatesr330]

i have the longrod 330,39mm carb, 39 tooth rear and running 20x11x10 tires.his bike is a stock 99 kx 250.i was in 3rd and he was in 4th and we were side by side until i hit 4th the he stated to pull but not by much.for some reason when i shift to 4th and 5th it seems like the power is not there (no power band).i can keep it in 3rd for what seems like forever and its still pulling full throttle but the upper gears just feel like im riding a 4 stroke.what can i do to fix this problem.thanks