Hey Guys. Slowly working my way to getting my daughters ke55 coupe on the road. The latest issue to come up is when the car is idling and the brake pedal is depressed there is a loud hissing coming from under the dash area, then at the same time the idle takes a dive and almost stalls the engine when the pedal is released the revs return to normal. Does this sound like a faulty booster or could there be another issue that relates to the vacuum system. Where do I start?

From your description almost definitely a dead booster.

Yep, agreed, most brake outfits will re-co them.

Thanks guys I will start making the necessary arrangements to have it fixed.