On a B model (no reservoir bypass) - During travel of flight controls or gear, utility pressure drops below 1000psi and both EDP and suct boost lites illuminate. NOT an indication problem (gear/flaps fails time check). EDPs, boost pump, boost pump supply hose, boost pump press switch,accumulator, relief and ground test valve changed out to no effect. Firewall valves check good. No mule available (hey, if it was easy....). Thoughts?