Does the line coming off of it hook into a vacuum solenoid, or does it loop around to the high pressure side of the turbo somehow?

The original .971 turbo has a vacuum wastegate. It's normally open, the computer sends vacuum to it to close the wastegate and make boost.

Some VWs with wastegates do something a bit different: The turbo has a standard pressure wastegate, which is set to open at like 10 psi. The computer uses a "vacuum" solenoid to regulate boost pressure to the turbo, keeping the wastegate closed longer so it makes around 14 psi.

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.