I'm sure someone can help me with an issue I have regarding idle speed. My W2 idles ok normally, drive around at 'town' speeds, no issues. I've noticed that if I push it over 4000 revs then the next time I return to idle it sits at about 1400RPM I.e. too fast. This doesn't change until I switch the car off and restart it, then all ok again - it doesn't need to cool down or anything for this to happen. Do I have an 'idle speed valve problem' or a 'throttle body' problem?