False mpg mfa readings??

On my '89 8v the mfa is working perfectly - apart from the mpg which reads about 12mpg no matter what -- tried resetting it with no joy -- car is actually doing about 35mpg judging by the last couple of tankfuls any ideas??

 

Think this might be something to do with the vacuum pipe, see if its connected, mine had come off in the engine bay on my last GTI and this sorted it.

Hope this helps

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Thanks I'll give that a try

 

Also, sometimes the vacuum unit on the back of the dials can be dodgy.