I've a 2004 Passat 1.9 Tdi (130bhp model) It has just done 100000 miles. I carried out a basic service - oil and filter, air filter and fuel filter. Now it seems like there is no power in the engine. Starts and idles as normal, no engine check light showing but is very sluggish and has trouble maintaining motorway speed.

 

The fuel filter replacement may have stirred up some crap and clogged the injectors a little.
I recommend using a can of Seafoam (if they have that where your from) to about 3/4 a tank of gas. If you can't find Seafoam just ask the guys at the parts store what fuel cleaner they would prescribe.