when i put my foot to the floor and get it higher then 4500 rpm i have a miss fire! but only happends if i put my foot straight down! if i accelerate gently then nothing happends! but also will only do it in 3rd, 4th and 5th! any ideas? i have replaced plugs, cap, and rota but still no luck! also it is not putting any codes in the ecu! HELP!