Hi there
This is almost certainly the Throttle position sensor - you can check the operation of the using VCDS / Vag Com in measuring block 01, if the unit fails you get the glow plug light and also a high idle at around 1155rpm, with no effect from the pedal. You will also have a DTC 10847 / P1639 "Throttle position sensor - implausible signal" or similar, get a code reader on it (preferably VCDS) to check.
Had the same issue with my 1.4Tdi and spent ages on it.
The sensor itself is up behind the pedal box, connects to the throttle pedal with a sort of spring loaded yo - yo attachment and is a bugger to take out, but possible. There is a nut and bolt on each side of it holding it into the pedal box, you can see the nearside bolt through the dash if you take the trim off under the steering wheel.
