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As for mechanical gauges, the only one I would ever get is boost. For everything else, go electrical. It's just easier to pass a wire thru the firewall instead of a hose or capillary tubing. When it comes to fuel and oil pressure gauges, a mechanical gauge's capillary tubing might burst and spray you with some nice fuel or hot oil, which would probably be loooooads of fun, especially if something were to catch fire.