The Hydroboost System is all hydraulic. I think the only thing electrical is the pressure switch and the brake light switch, the latter not really part of the Hydroboost System.
Here is a link to the P30 manual which describes the Hydroboost operation and troubleshooting:
http://www.gmcmi.com/wp-content/uplo...sis-Manual.pdf
I'm currently troubleshooting weak braking...
Hope this helps,
Brian
1992 Holiday Rambler Imperial 35'