I am having this problem. Installed the 74 mm throttle body and MAF ( putting the original MAF sensor in the new MAF body) and the car idles fine when first started. however, after a bit of driving the idle will go between 1500 and 2000 on neutral. if changing gear, it will accelerate itself after pressing the clutch. I used the black RTV gasket maker along with a new oring on the throttle body. I guess its back to checking the connections and re adjusting the throttle body. Hope this gets solves.. i dont want to go back to 68mm...