High idle problem with 2lt engine Options

[Creamsicle New Zealand]

Hi all, I'm wondering if any one could help me with a problem I have. When either cold or hot my engine runs at 1600RPM. I have looked for any air leaks, all the hoses are new. The only things I can find are the following - After removing the throttle body I noticed the surface the gaskets sits on is uneven due to powder coating so I sanded this area back to bare metal and it is a lot flatter, this had no effect on the RPM. When the engine is cold I can block of the air hose going to the cold running injector and the revs come down to about 1200RPM, as the engine gets warm the cold running injector stops operating as it should. The air intake valve on the side of the throttle body is wound fully in but the valve does not appear to seat properly, when I hold it up to the light I can see gaps both side of the valve, is this normal?
The other thing I noticed when holding the throttle body up to the light was the butterfly valve in the throttle body has gaps around most of the sides of it when closed, is this normal or is this an indication of wear?
In the butterfly valve is a hole approx. 3mm. When I block this off the revs come back to 1100RPM which is getting closer to what it should be.
Any one have any thoughts on this please?
Thanks Steve