[NachtRitter]

Yes, absolutely! Two relatively simple things you can do with the TDI: 1) improve aero (since the TDI runs relatively cool, you could block off much more grill than the equivalent gasser), and 2) get a taller cruising gear ratio so that you are running in the engine's most efficient range (between 1800 and 2000 rpm IIRC) at a higher speed (a 5th gear swap for the 5-speed, or a conversion to a 6-speed tranny)

However, of the models readily available in the US, it is the used TDIs (the Mark IV's with the ALH engine) that will get you the very best fuel economy... so if you are looking for a new car, then you won't see the same FE from the TDIs.