I think they are electric. The back of the gauge only has 2 wires, and no vacuum nipple. I think it's specific only to S15's too. You can use the holder in S14's though, but you have to cut the top bit of the plastic to fit.
Anyone has the Wiring Diagram for the Bee-R rev Limiter?
and any one using it? how's it on a rotary? hehe... is it good or bad?
any suggestions? i have one unit.. but dont know if i should put it on or not as i know...