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.
He's at it, yet again. This time could be his best and in ultra-spectacular Hollywood set, style and props!. As for the Ford Fiesta, it might be road illegal, but how much does it take to make one's car sound & go...