Wolfgang, just out of curiosity, does your 2009 4/4 already have throttle via wire control? Probably yes when talking about the throttle position sensor. My 2014 has it but I haven't had the problem you describe. Have you tried if on a good new road the throttle is also unstable when driving slowly? Is the accelerator still screwed down properly? It could be that the screws have loosened a little and the control of the foot has become worse when the linkage in the housing wobbles.
