What is going on here???? (turbo pump on an NA??)

[Naturally Aspirated]

So an acquaintance showed me his 1.6NA 1991 jetta engine to help solve what pump he had and i came accross something i have not seen before. From the pictures below it looks as though a turbo pump with the aneroid (or whatever its called) is hooked up to the vaccum for the brake booster and some sort of blow off valve. Any ideas why this was done? He bought it this way and says it runs well. I was wondering the advantages

[theman53]

Merffy on here has the same deal. Only one I have seen, but it might be the alt. compensating pump that I have heard about. It does work similar to a TD pump only with vacuum. There is a pin with a ramp in it.

[R.O.R-2.0]

it has vacuum hooked up to where the vent would be on a TD pump..

maybe as the engine revs go up, it sucks the diaphragm down, and increases fuel?

[theman53]

yep. that is how merffs works. There is a spring and starwheel just like a TD as well. It is kinda different:D

[R.O.R-2.0]

looks to be factory too?