Hey guys, Im having some trouble tuning this engine.. Heres where Im at:

The temp is ok, we dont have any fancy gadgets to check, but a drop of water on the head shows no signs of bubbling whatsoever..

However, whilst driving the car, when i release the throttle, the RPM stays up and doesnt go back down to idle until I hit the brakes or dont touch the throttle for a few secs..

Just a note, im using a crappy AM radio which has literally no functions on it but throttle, brake and steering.. Could this be a factor?

Thanks in advance all !!