How to build a circuit that holds power on a component by using a latching relay

Circuit is energized with momentary connection at PB1 (normally open push button).
Circuit is deenergized with momentary open of circuit at PB2 (normally closed push button).

We used one of these with a nitrous oxide system that was activated by an RPM switch. The problem was that when the RPM switch shut off the N2O the RPMs would drop back into the range where it would be reactivated resulting in a series of on/off cycles instead of a clean shutdown.