How do I troubleshoot my brake booster?

Usually, if a booster diaphram goes bad, you will have a vacuum leak when you step on the brake pedal. That will affect the engine idle causing it to idle higher, rougher, and sometime make the engine die. The valving in the booster can sometimes go bad too. The pedal going to the floor is a different problem.....probably internal master cylinder fluid bypass, air in the lines, or an external fluid leak somewhere.