Brake booster issue

You must be refering to the master cylinder. Brake booster is vacuum operated and does not use any fluids. Yes, master cylinders can fail internally with minimal or no leakages.

Yes, What is it doing? Try this while engine is off-pump brakes a few times hold in and then start car-did the brake pedal drop inward?

It's giving the hissing noise when the pedal is depressed. It's like stopping a non PB vehicle. the abs motor, is functioning correctly(it's pushing back on the pedal when brakes are applied)I see no fluid leakage anywhere. Fluid is a bit dirty, but still where it belongs. Valve on the manifold, and booster work fine, no leaks in the vacuum hose. A true quagmire

The brake booster diagphram has ruptured

So, that being the case. Why can't I find a rebuild kit for it. if you can buy rebuilt boosters from auto stores, someone has to sell the kits

You have to replace the brake booster-I don't think it comes with a rebuild kit-