Tachometer (maybe) fixed
I was instructed to try cleaning the tachometer ground wire to stop it from freaking out on me, so that is what I did. It involved removing the rear parcel shelf wall, which was very easy after removing the four screws that hold it in, located below the net hooks. The wall pulled forward, and the ground was behind the passenger seat above the relay compartment. The ground wire that was there needed a cleaning, as the metal had that fuzzy white look to it. I took sandpaper and cleaned the contact as well as the nut holding it on the grounding bolt. After everything was replaced I took the car for a drive and had no tachometer problems. Hopefully the issue will not return!