1) The plug on the right is for the engine temperature. What is the plug on the left for?

http://roughtop.co.uk/john/smart/3.jpg

When unplugged I get P2520 error code logged which is supposed to be "A/C request A circuit low."

I suspect it is maybe a valve to shut off the heater matrix when the AC is turned on but would like someone to confirm it.

2) I think this is the wastegate solenoid

http://roughtop.co.uk/john/smart/1.1.jpg

When unplugged I ge t P2425 Exhaust gas recirculation cooling valve control circuit open". WTF

3) I think that the EGR control valve is just down to the right of the air box:

http://roughtop.co.uk/john/smart/4.jpg

You can't see it on that pic but just down there behind the inlet piping with the air filter just on the left.

With that unplugged I get "P0243 Turbocharger Wastegate Solenoid A Malfunction".

All of which when put together leads to a state of confusion. I did not use Xentry for this as I am having a few problems which I am sure, if you have ever installed Xentry, you will completely understand.