Take a look at these two articles, they may help.
http://www.dieselgiant.com/mercedesaldaboostsystemservi.htm
http://articles.mbz.org/engine/diesel/alda

Hope it helps and yes there are other things that are good to do on the engine but keep at it and do them all. With doing all the things people have listed it can be surprising the difference it can make.

__________________
1983 300SD
200000miles