OK, on gage operation. Essentially, as said above, the 5v gage regulator (called a 'voltage limiter' by the factory) is getting power all the time; its power should be cut off when you cut off the ignition switch. So, as Bill indicates, there is a short somewhere, or someone messed with the wiring in the past and got it wrong. If shorted, that is cause for significant concern, and needs to be run down and fixed ASAP. (I would keep a fire extinguisher in the car 'til this is fixed.)