strange reving problem

I have a UK 1.8 Zetec 2000 model which as the car comes to a holt the engine speed increases on its own up to around 2000rpm, only when the car comes to
a complete stand still will the revs return to normal. A few months back it was much worse it would rise to about 2500rpm then at a stand still stall or almost stall. The ford dealer replaced a split pipe (not sure which one ) which seemed to cure it for a while.
Anybody know what could be causing this & an easy quick diy fix to save me the hassle of taking the car in to the dealer?
Thanks in advance
John.
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Likely you have an intermittent vacuum leak or something similar. Two possible culprits are the fuel vapour recovery system and the EGR (exhaust gas recirculation) valve. Unfortunately there's no easy or simple home fix for either.
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mine does that also. Hit 3500 once. Usually worse when aircon is on, although often happens when hot anyway. Never happened in winter.
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