I just purchased a 91 Allante, my second Allante, with no brake assist. After diagnosis with the factory service manual, I determined the electric, hydrallic pump was weak. It would run the whole time the car was running, never strong enough to charge the ac***ulator. Verified this with Hussey at Allante source. Replaced the pump and relay and within 30 seconds the brakes were fixed!! Just a thank you for this site and people like Stealth and Dick Hussey.

BOCH III ABS pump and relay

were both the pump & relay bad?

if not, save that relay in the spare wheel compartment .. there are none out there except for donors.
every donor car I come to, has the whole system out of it, including the relay.

when the relay goes, it goes .. no warning.
if you dont have a spare with you, its flatbed time.

No, just the pump, but as you have said "get the relay if there" so now a spare is in the car!!