When I changed from the 48mm trottle body to the 52mm I was advised by this forum to turn on the ignition and depress the accelerator 25 times to let the ECU reckonise the new body. I did this and it worked fine for many years. With the emissions so high at the last NCT Test ( Your MOT ) I decided to get a new 52mm body and its the new one that's revving high. The car never went on diagnostics. I will try tomorrow to hold the pedal down for 30 secs or so with ignition on and see how it goes. It has'nt over revved since the NCT and had her out all day Sunday on the motorway.When you renew the throttle body or the IACV valve, it MUST BE SETUP corrrectly on T4. There is no other way to set it up other than on a T4.