Did the garage set the car up after Temp sensor changed, were they "Familiar with the Bosch system "....Hear are the readings for a good " Yellow Temp sensor" ..Cold engine 15-30 c...1.3 K..to..316 K..Ohms........Hot engine...80c & over.....250-390 Ohms...get this re-checked. The engine High RPMs ...first check Throtle is returning fully at the manifold -[ rarely gave trouble] back in the day....under the intake manifold you have the idle control Valve, with the engine running ONLY there must be 12volt at this unit, if not the idle will be very High as you have, at the same time the 2 Hoses on the unit must be inspected fully for leaks / perished hoses as this will cause High revs, to test the Electrical side of unit it has to be removed, once removed 12V aplied to the terminals after 5 / 9 mins one should not be able to "Blow" through it....ie the internal Valve one would see fully closed....... i wonder if the Garage went for road Test after fitting the sensor ??....as you say on driving Home...Revs High....Last i would say get a "Co mixture" check done on a Hot engine only...should be 1.5 to 2.0...get then to watch the readings for "Eratic readings...goes up..then settals...then up again...sure sign of leaking injector, Co must be steady reading, do you feel the garage might want this infomation ?.....with respect to them. Also all Turbo piping must be in good condition, as any leaking will effect engine running. best i can say. Peter