My golf 1.4 has recently had a new fan switch and thermostat because the car was overheating. During it's time when it was overheating the revs on the car would begin behaving erratically when i was driving and would occur as the car crept over 100 degrees. Now i've had the above various replacements my car still revs erratically but when the temperature is around 90 degrees.

Can anyone tell me why this is happening still as the car no longer overheats but still seams to share some of it's overheating tendencies? I'm really puzzled!

thanks
Stuart