I just purchased a used '97 Suburban ('kinda hard to buy '97s new any more) and it came with a brake problem.

If you push the brake pedal in before turning the engine on, or you press it all the way to the floor (sitting still or driving, doesn't matter) the pedal will stay down and the brakes will stay engaged. The only way to get the brake pedal to release is to turn the engine off. After the engine is turned off the brake pedal will reset and will then operate normally until the next time it is pushed all the way to the floor.

I've done some searching and every problem with a similar descriptions is answered with "bad brake booster." The brake booster was replaced by the previous owner recently so I was wondering if there was anything else I could check or if there is reliable way of testing the booster before I go and replace it again.