The car... an ABF in my mk2

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On the motorway it runs perfectly fine
It also runs fine when starting from cold in the mornin, the problems happen much much more when running for 5-10 mins.
Setting off from traffic lights it misfires, sounding like a subaru
When cruising along at 40 in 5th it's usually fine and runs smooth but if i put my foot down it goes into subaru mode and the same happens if the road starts to incline, meaning I have to gear down due to the loss in power
I've heard something about vaccum pipes or something like that might cause this??
Any help would be much appreciated
