Looking to buy a working turbo for my 94 940, let me know if you have anything, thanks.

First of all, im glad i found this site, it seems to be a great volvo resource for us dyi guys. We've owned a 240, 740, and now a turbo 940. My question is where is the turbo gauge connected to, or what feeds it. We recently had the turbo rebuilt, and now i can hear it spin but the turbo gauge only ...