toyz: none. They're all there for a reason. If you start killing systems on the car, you'll start having running/starting issues. The vacuum system on this car is bare bones, and comes stock with one of the smallest systems of its day(take a peek under the hood of an '88 Prelude sometime, you'll see what I mean). Removing parts of it won't help you in any way. Fixing it so it operates correctly, on the other hand...
Boosted88: I think its for the BOV? I don't have a turbo car, so not really sure...