I have a 2000 z24 cavalier 5spd aftermarket cold airintake. i have a problem with the rpm.?

just say im driving down the road when i push in the clutch my rpms will go to 4000 rpms but it self, and will stay there until i slow down to 10 mph, it wont rev high if i dont go past 10 mph, it only does it when the clutch is in and im driving, it wont do it if im not moving or if i only going 10 mph, i replaced the idle air control vavle, the throttle position sensor, clean carburetor. replace the map sensor. i took it to a shop and they first said it was the map sensor bec the code came up, but it didnt fix it then i took it back and they said it was in my cars computer.. well thats about it thank for the help