accelerator problems

I have a 2007 4.7L Flex 4x4. When coasting (not accelerating, just keeping an even speed) at either between 35-45mph or 60-70mph (could be other ranges too, these are the main ranges I stay in for extended periods), my Jeep will suddenly accelerate a bit(as if I step on the gas for a moment)...

I have a 2007 Commander, about 2 months ago when pulling into traffic on a highway, I need to accelerate to "get up to speed" when I let off the gas the vehicle continued to accelerate on me, braking does not work to slow or stop the vehicle. I took it in, had a new trottle kit put in, and it...