Done a bit more digging - seems like it may be a faulty EGR valve, so will investigate that further.

This has been a really interesting thread - I've only found it today. The lack of power problem is similar to the problem I've got with my diesel mondeo, but I don't have the glowplug warning light and nor does the engine cut out. Does anyone know if the symptoms I've got - see below for details - are a precursor to this glowplug/cutting out problem? Or have I got a different problem ?? If so, anyone got any idea what it is? Many thanks. Ford Mondeo II estate, 02reg, 113k, 115hp Duratorq D6BA engine. Symptoms:- distinct lack of power, feels 'flat', really struggles up long motorway hills at 50mph, in third or fourth gear, smoking more than usual, esp at high speed (80-90mph) when significant clouds of smoke can be seen. Struggles at 70mph or so on the flat or on slight inclines on motorway and A roads, difficult to overtake other vehicles, no acceleration possible under these circumstances. Engine revs freely when not under load (ie not in gear), but under load it struggles. A regular 'kick' or 'cough' can be felt between 2800 and 3000 rpm, as if the engine is not running right, and it simply doesn't respond/accelerate like it used to . The engine seems slightly better in the morning than in the afternoon, though I understand this is normal as the cooler air gives a denser charge than the warmer air in the afternoon. So this may be irrelevant I guess ?? Car has been serviced regularly, there are no warning lights lit and the temp gauge is normal. I've thought of changing the fuel and air filter to ensure sufficient air and fuel are getting through, but as these are changed at the appropriate service intervals I doubt this will make much difference. Of course, don't know for sure until I try!