Checking and optimizing the fuel supply pressure in the base of the injection pump will give you some additional power. Especially if it is substandard now. There is a pretty comprehensive thread on this in the archives.There are other possible benifits as well.

Some simple things like making sure when you press the pedal the injection linkage advances the lever on the injection pump to its stop. Common complaint as the linkages parts age.

A 240d has to be kept in optimum tune to be practical. It is one of those cars that basically you want everything that is avaialable powerwise. A 0-60mph timed run is a starting point on a flat surface to see if you are currently sub standard or relatively normal at present.