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.
any supercharger sifus out there...
if i'm gonna buy a levin engine w a supercharger,
wat particulars do i hav 2 look out 4?
can u sifus teach me how 2 know whether its in good condition or not.
ur info is very much...