stalling, idling rough

This one has me a little worried. Many people here talk about the rough idling of their cars (mine is a 1980 300SD). Mine has been doing that and I have contemplated trying the dampener screw.

Today though it is stalling out. It will idle not too bad in neutral or park, but drive with the brake applied - it stalls.

Hoping this isn't as bad as I think it could be.

Seems like it may have lost some power as well lately.