Due to the fact the dpeed drops when the valve is disconnected it shows the valve to be working.

Rather something is telling it to open when at running temp, it could well be as said the CTS, these go out of range over time and thus give false info to the ECU, do it seem to be overfuelling?

Is the base idle set correctly, i.e. when at running temp and the valve disconnected AND all electrical equipment switched off, you want to see a speed of 850-900 RPM.

It can also be down to a bad TPS calibration, which is fairly easy to check.

It should then raise and drop back again when the valve is reconnected (obviously not at the moment, in your case)

Martin