Ah. We can safely assume your ALDA is not a virgin then. They come from the factory with a plastic cap/seal over the screw, not something that pops off and gets lost, as the Gods of Bosch aren't keen on owner servicing of their lovely pump. On my old SD it was black, others say theirs was silver/grey.

This does not necessarily mean anything. Only one out of the four turbodiesels I have owned had the cap still in place when I got it.

Try IP and Valve Adjustment
 

I've had my 300sd for 4 years. biggest difference in power i found was valve adjustment (Mercedes Diesel Valve Adjustment Procedure) and IP timing (Injection Pump Timing Adjustment for Mercedes 617 Engines - Topic)

... another bump for an old post... why? it's like you are looking for low power threads, and injecting your opinion on the solution... to threads that are years, nearly a decade old on one case...
I"m thrilled you found power from a valve adjustment, and IP timing set, but MOST turbocharged motors lose power when the fuel enrichment device (ALDA) does not receive the boost signal to add fuel...

............one post out of hundreds that don't belong on a specific thread or have been posted without any investigation or forethought.

Why pick on this one?