I'm posting this as I think it might help others with a similar problem. The throttle On the VVTi runs using a drive by wire system. There are 2 sensors, one on either side of the throttle body. Looking in under the bonnet, the one on the right very rarely ever gives a probem, but the one on the left that has the cable attached quite often does. If the VVTi has an achilles heal this is it. I'm on my second one (but then I have had the car 9 years) I had the engine management light come on pretty