Any ideas on how to troubleshoot a wonky gas guage?

There is a fuse under the hood in one of those white inline fuse holders. Same thing happened to me a few years ago, its in your owners manual.

Add gas to the tank. :D Just kiddin' ya. In my 93 Formula Plus I had the sending unit go bad. Just my .02.

Rob

:D I will sell u a gauge out of a 92 mach 1 for $10.00!!! :inlove: