I'm getting a CEL FF-A1 = Control Unit Supply.

I assume this is the power supply to the ECU?

I'm getting this CEL after completing my battery cutoff switch. Car starts fine.
I used 10 gauge wire to connect the small wire from the battery to cutoff switch, to the junction box.

Should i worry about this CEL? if so, what should i look for?

Thanks
Franklin

Go through the wiring diagrams and put a small gauge (20-22ga) wire from the continuous power lead at the ECU directly to the battery, bypassing the cutoff switch. OBD2 cars usually have a problem with a cutoff switch, while OBD1 will record the power failure but doesn't care about it much.

That, which may violate the rules, or just don't use the kill switch as the means of operating the car.