Hey guys, hope everyone's Monday is better than mine

My GQ TD42t has started over idling anywhere between 1000 to 1800. Its got me a bit stumped on what the problem actually is. The problem comes and goes and seems to be correlated to idling high on start up but later on disappearing once driving for awhile (but its still very random). I've tried adjusting the throttle cable with no luck, disconnected ac idle up solenoid and checked for vacuum leaks. Any ideas what else to look at or have I missed something somewhere.

Cheers,

Tim