Knock sensor - angle important?

How important is it to get the angle on the knock sensor correct? If yes, what is the correct angle?

97' 540i

No angle.
All it senses is "knock".

Bentley says to note the angle of the old one before removal, and install the new one at the same angle, using a torque wrench, FWIW.

Definately torque these down to the proper specs. It's one of the only items that is critical that you get it as precise as possible. It's a piezo electric crystal that generates its own electricity based on vibrations. Their sole purpose is to detect detonation, or knock, which creates a very specific voltage because it emits a very specific frequency. If they are not torqued properly it could throw off the readings sent back to the DME and it may retard your timing because it thinks it's experiencing knock, when it isn't. Don't be lazy and use a torque wrench.

Is torque more important than angle?

Same.

Well, the Bosch knock sensor senses knock, so install it close to the angle from factory, but it is not crucial even if it is off a bit.
As Ryan said above, it is piezo electric device so it can sense shock in either orientation.

The torque is a different ball game, it is important whenever you fasten any nuts and bolts.

The big thing to remeber with the tq on the knock sensor--over tighten and the gizmo will be retarding
ignition at all times--they must be tightened to the factory spec--on my Volvo that was 11 ft lbs--along with that it was suggested that the bolt holding the sensor should be coated with a green loctite thats for electrical
devises.--