Not sure what they did in 94, but could it be possible that this is the line to a vacuum dump valve for the speed control. I know Ford along with others used vacuum switches on the brake pedal bracket that would dump the vacuum to the speed control servo in the event that the brake lamp switch failed.
Most-all speed control systems have a redundant type safety switch to disable the speed control system in case the other one fails. Some were vacuum type (mainly for older systems) others were brake pressure switches ( hydraulic or electric )
Just guessing BTW
98 12v, 48RE, Revmax kit, V/B, triple disc stage 5, ultra low stall with a few other billet pieces. AFC modded, 100ish plate, 16.5ish*, KDP gone, 60lb springs, 4K-GSK, BHAF, pyro, trans, boost guage. , 72 AM general M35A2 LDT465