The turbo on my 1993 300D 2.5 will spool up and whistle when revved at idle, but doesn't boost when driving. Also, transmission shifts quite hard, and air flow in the cabin is stuck on defrost. What missing vacuum lines would be causing these three problems?

I have checked all the superficial lines, but there are more they could be worn, loose or broken. Where should i check first? I can't seem to figure out what is going on.

Help would be much appreciated..