Anyway, getting back on topic......
A thought occurred to me this morning and that is that a wrong fuel to air mixture could be caused by a faulty lambda sensor. I was thinking back to when I was helping Ed (Leeds_Finest) out with his T5 back last year and his car was 'surging' although worse than mine. One of the things that had to be replaced was the front lambda sensor and if you look at the service schedule for most cars, O2 sensors are a service item or at least they were on my Dad's old Skoda VRS.
If the O2 sensor is sending dickey readings to the ECU then the air to fuel ratio could be wrong and the ECU thinks the mixture is too rich. In laymans terms, it then tells the fuel pump to pump less fuel in and perhaps that would explain the feeling that the car is under-fueling.
I still think that 'ringing' or whistle sound is something to do with the problem and at least changing the vacuum lines will either prove they are at fault or rule it out as a cause. No harm in changing them either way.
This car has done wonders for my problem solving skills.
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