89 325i Cabrio SI Board & Fuel Economy Gauge Issues

[89Cabreeo]

In order to work on the wiring for my trunk light and add a second one I disconnected power by pulling fuse 21 rather than fully disconnecting the battery negative terminal. Not sure if either way really made a difference with this issue. Over the course of working on the lights I had to restore power and pull the fuse at a few different times to check the circuit and ensure I didn’t short out by grounding a hot wire or connector. After all was done and took it out for a spin I noticed right off that my Service Indicator (SI) lights were all out (greens, yellow, red) and the SI “Inspection” light was lite. Also noticed that my Fuel Economy Gauge (MPG) was ghosting on me, i.e., needle sitting at max on the left foul line typically while cruising and then all the way to the right foul line at zero when I got on the gas, never ranging anywhere in between as it normally should. Both the SI Board and the MPG gauge are on fuse 21 and, of all devices on that circuit, they are the only ones malfunctioning. Prior to this the SI lights were functioning normally and I was down to 2 or 3 greens at start up.

Is it the whole SI Board?
Is it just the SI Board batteries?
Is it the Fuel Economy guage?
Did I confuse the SI Board by taking power on and off a few times?