The electrical boost gauge uses a three-bar MAP sensor to get its readings. The sensor must be fastened according to the position in the instructions in order for it to work properly. We secured ours to this dash support right above the fuse box. If using the mechanical boost gauge, you just have to run the airline into the engine compartment and find a suitable source for manifold vacuum. Both gauges come with vacuum T-fittings and rubber couplings to accomplish this.