Hi. i got rid of powermaster awhile back. I got a junkyard cutlass vac booster and it went bad pretty fast and now hisses with pedal on and has little assist.. I replaced the check valve which was already ok. Last time i went down track the brake lights came on while at WOT..i guess boost was getting behind the diaphragm? I see that the parts stores have the booster for $$$ over the regular g-bodys but i guess thats a power master but cant verify. Thanks for any ideas. Rick