Throw caution to the wind and treat yourself to premium diesel instead of the usual bilge-water served up by supermarkets, for good measure chuck in a bottle of fuel system/injector cleaner and listen to how smooth your car's engine runs and let the increased performance put a smile on your face.

 

It's as good as getting a new car... almost!

If you're still driving a BMN with the plastic, flappy inlet manifold, bin it and fit a nice alloy BKD one sans flaps.   Then have it remapped and revel in how smooth and fuel efficient it has become.  

 

My remapped Mk5 Golf 170 TDI would return c. 52 mpg driven hard on long trips which I thought was remarkable for a car with 210 bhp and 330 lbs-ft. 

I think @MicMachas a 1.9 BKC 105BHP.  They just go on and on and do feel quite sprightly when pushed a little.