940 turbo help

[turbo940]

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 goes to half way mark, and not on the white section that indicates that the turbo is actually working. thanks in advance. Take care.