Hydroboost?

[njdevi11]

I've got this hydroboost from a step van, It's got 4 fittings on it, does anybody know how to hook this up? the only other hydro boost's I've seen have three.

Is this supposed to be plumbed like this?
high pressure: pump->Hydro boost->gear
low pressure: gear->hydro boost->pump return

[grancito]

I've not seen one like that, but see if the two top ones are connected, it may only need the small one to be plugged.