Have you considered it might have been a vacuum leak, and the buzzer warning of low vacuum for the brake booster? You should have a vacuum storage tank that will provide boost when you are on the throttle, but maybe the vacuum was escaping before you wiggled things?
Looks like he has hydraulic boosted brakes from the power steering pump.
Have you replaced that sensor yet? I replaced mine today....no more alarm. It cost $9.00 from the local International shop.