Im adding a Powerdyne Bd11 blower and im wanted to mount a few guages in the center A/C vents. I have two guages on the A-pillar, Water temp and oil press and there both electrical. There Phantom Guages and i want the boost guage to match and the only way is to get a Mech. Boost Guage. So whats the difference between a mechanical and electrical Boost Guage. I know the difference with water temp and oil pressure, you have to run all those lines and stuff, but how does a mechanical boost guage work??