Okay, so as I'm driving, and only occasionally, I'll accelerate pretty quickly to about 40, and then without me changine how I'm accelerating or driving the engine will get quiet, and slow down in it's acceleration, and then if I increase how much gas I'm giving it, it still only accelerates the same "slower" speed, but if I really push it, then it kicks up and flys. Suggestions? Reasons? Normal?