about to install turbos on my 350 tpi L98, Just wondering how do vacume controlled componets work under boost. (a/c controls, egr) and what if anything needs to be changed?

 

You need a working check-valve between the intake and the vacuum reservoar (Black round ball)

 

Thats it, just a check valve, i thought it would be a little more complex than that. Where can i get one ?

 

Your car should have one on it from the factory. They put the check valve in there to controll the vacuum devices when you are at WOT conditions (such as climbing a hill where intake vacuum is low). I didn't do anything to my turbo cars vacuum hoses, except put clamps on a few of the larger ones to keep them from blowing off under pressure (small zip ties also work well to retain the smaller hoses).

Edit- in case you are wondering, it is on the RR corner of the intake plenum, right near the FPR (at least this is where it was on my car). It is usually a white/blak plastic device in one of the vacuum lines. To make sure it works, start your engine for a few seconds. Then shut it off, and remove the vacuum line from the vacuum reservoir. If the check valve is good, there will be vacuun stored in the reservoir for several minutes after the engine is shut down.

Oh yes, another vacuum device to keep in mind is the PCV valve. I would either use a positive sealing valve like used on the Buick GNs, or just eliminate it and run valve cover breathers. I have done it both ways with good results (though open breathers tend to make a little oily residue on your V/Cs).