I can not speak for the Blackhawk conversions but I can speak for new C-90's as they leave the factory. So keep in mind that an older c-90 may not be as tight. The leak rate, meaning both bleeds off, at 4.5 psid should be under 3000 fpm. This of course checks how good is the pressure vessel. As for the power idle check this is a check of the flow packs and the aircraft should hold max psid single sourced, meaning only one bleed on, all the way down to 85% N1.

As I have stated this is on new aircraft as they leave the factory, older aircraft may not be able to hold this.