I received the throttle body in the mail yesterday from David Askew. I just need to get some gasket sealant (I'll pop and get some this lunchtime) and I'm all set to install it at the weekend.
Hopefully everything will go to plan, the leak will stop AND my CO emissions problem will be solved! I'm kind of hoping that the high CO has been the result of the leak, with the engine running richer than it should due to this leak in the throttle body. It seems that the Ghibli ECU is not set up to vary the fueling map based on actual measured inlet pressure, but that it only varies fueling based on throttle position and temperature?
Since the car is scheduled for its big service on Tuesday, if there's any problems or fine tuning required then I'll ask Jorrit at Auto Forza to sort it out. To be honest, I'm tempted just to ask him to install the replacement throttle body? I'll see what the weather's like this weekend... since I also need to paint the new house!