My dimmer does not work with the Omori gauges. So they're either on or off. I used the clock harness. But I did not try tapping another location, YMMV.
does that mean your gauges are lit all the time? Basically if, they're working, they're lit?
Is this how you wired it?
From Omori NA Electric Boost Gauge installation instructions:
Connect the red wire to switched power, on only with ignition. Black wires to ground, white wire to illumination. (Powered only when headlights are on) Tape the brown wire back to the harness, as it is unused.
It sounds like if the white wire is connected to the dimmed light switch, the gauges should dim, but since I don't have the gauges, I can't try it. Did your gauges have all the wires listed above?
And, yes, I know that my warranty will be nil if I open the gauges up... but since I'll be ordering from Malaysia anyway (unless Omori NA gets their act together in the next week or so) my warranty will be pretty much non-existant as it is...