I have a 1991 940 Turbo that I bought two weeks ago. This is my first Volvo so I'm slowly making my way through different aspects of the car. On the dash, there's a gauge marked "Turbo" with a needle. The needle just stays in the middle. What should it be doing?

 

it is not hooked up then.

It shows the vacuum and boost.

 

Thanks! What, though, is it supposed to do? Should it move left at idle and right when I accelerate?

 

The black zone shows the vacuum.
The white zone show manifold pressure (boost).

It is not only in black during idle. it is based on the load on the engine, depending how opened the throttle is, it can stay in the black while you're on the freeway.

It better to be within the black with a steed foot. you get better mpgs that way.