I recently got my cover valve gaskets replaced and after it was fixed I was driving on the highway and when I took my foot of the accelerator my speed would stay the same. (like the cruise control was on). when I pressed the brakes it would go down as usual. but, when I was stopped at a light the RPM was at 1000 and it was creeping up and when I took my foot off the brake the car would jump like the gas was being pressed. It started to get a little high for my liking and I put the car in neutral while I was stopped and the car suddenly revved up on its own to 7000rpm. I cut the car off immediately.

It has done this twice and there isn't any apparent problems with the throttle getting stuck or anything. Any help or suggestions??