I went the lazy route and bought a fuse adapter for my boost guage. Just a wire mated with a fuse that would go into your fuse box with a male and female end on it, so you can stack fuse adapter with headlight fuse or what have you. Havent installed it yet. BTW, while I have you all here. Where would be the best or cleanest spot to put your grounding wire on for a boost gauge? I am doing a steering column install.
See following pic for an easy ground location. I actually used this pic for an alarm question, so the orange arrows are all over but look over to the left near the steering column. You'll see two grounds connected to that area in one spot; one for boost gauge and the other for a turbo timer.
Also, I wired my gauge up to the foglight relay. Automatically comes on when I turn my headlights on since I normally always keep the fogs on anyway plus I can turn the fogs & gauge off for more of a "family car" look at night from far away. Also kinda cool to be at a light with a car revving, look over and hit the fog switch to light up the gauge and a bit of road in front of me.
New 2025 CX-5 with highway vibration problem; tires?