SKODA 1.9TDI down on power...?

Need some opinions please...!

I have a 2005 Skoda 1.9TDI (100BHP). 55k miles (88Kms) on the clock. FSH, and recently serviced.

The car has never given any trouble from new, except in the last couple of weeks.
First I noticed the idle is too high, not very much but enough to be noticed....
Next, a few days later, when on the motorway I notice what I can only describe as the engine sounding uneven at speed, and I mean just around 120Kph.
And today, it was down on power bigtime (OK in the low gears only) and sometimes would hardly pull away at all, almost completly flat, but it improved after a while, but it's definitely not as good as it should be.

There's no smoke out of the car, but I do have an orange light on in the dash for a while now, something to do with the exhaust system acc. to manual.

So, any thoughts,
Thanks in advance... PCOCP

My initial suspicions would be a dodgy mass airflow sensor or MAF. These tend to fail in two ways primarily :

1. Use of an after-market "oiled" air-filter with too much oil applied or oil applied to the "clean" side of the filter, contaminating the grid of sensor-wires
2. Bad electrical connections from the sensor back to the ECU

In case (1) above some people report successfully cleaning the sensor-wires with arklone or perklone (dry-cleaning fluid) after removing the MAF from the car.

In case (2) above I've had success by applying a generous blob of Servisol silicone grease (available from Peats / Maplins / etc.) to the electrical connection block that plugs into the MAF. Unplug the block with the wires from the MAF, put a blob of Servisol across the three or four holes in the block and plug it back in.

To eliminate the MAF as the source of the problem, start the car and note how it runs. Switch it off, unplug the MAF electrical connection block and start the car again. If the car runs the same, the MAF is probably the culprit.

You will need someone with VAG diagnostics or a code reader to reset the ECU error-codes and eliminate the orange light.