On the way to Cornwall on holiday last week, after a goodly run on the motorway/dual carriageway, the next time we pulled up at a junction the idle was lumpy, hunting from about 8/900 rpm up to about 1500 and back. No obvious signs of distress otherwise. After another day or so the engine warming light came on.
The local place I took it to diagnosed and replaced a faulty Manifold pressure ("MAP") sensor but also said that whoever had last replaced the fuel filter had replaced it with one with too low a pressure, marked "3.0 Bar". They reckoned this had caused the fuel to run a bit lean and replaced the spark plugs too as a result.
It's marked as a Mann Filter WK 69/1 Made in China, along with the 3.0 Bar and blue date stamp of 0912; but that's all it's marked with. He's replaced it with a Fram G10243, "Cross references Purflux: EP207, Volkswagen 1K0201051B/1K0201051C" I think, as that was the box he returned the old fuel filter to me in.
Before I go back and have a go at the garage who fitted the fuel filter originally, does this sound right?