Hi chaps,
I know it is an older topic but only just registered.
I had a similar problem on my xkr, somtimes ok then others stuttering during accelleration and hunting during kick down gearchanges,
Anyway to cut a very long story short by accident I noticed that the air intake duct on to the throttle body was a easy fit, so initialy I wrapped insulation tape around the perifery to build the diameter so it was a push tight fit with the air intake.
What a difference it was like driving a different car so it must have been a small air leak causing the problem,
fitted a new seal and it is a nice forced tight fit so give it a try all it costs is half an hour and some insulation tape, Oh and let the ECU sort itself out on initial start up.

regards
rrosscoe :