Just purchased a Canadian 97 Jetta TD .... and while changing up the air filter i found this disconnected.

disconnected parts

hook'em back up

What does this puppy monitor ... I hooked it all back up ... and went for a spin. I didn't get any lights flashing in the dash.....
but if i felt anything different it felt like it was coasting longer from 100+ km/h
looks like it was connected between the turbo-charger and the vacum line that goes to the front of the engine that splits to the brake booster.