Alright I really need help with this one because I've exhausted my resources. Here is the issue, I bought my 1993 del sol si about a year ago from a friend of mine. After driving it for a while I realized that the brakes were very spongy and at a stop light the brakes would sink to the floor. Alright, well we replaced the master cylinder and 3 out of 4 calipers, the master cylinder was bench bled and the system was bled several times. The master cylinder was a remanufactured one from advance auto parts because the dealer around here is a dick to deal with. Alright, well the pedal does not sink to floor anymore, however, i still have only about a half pedal that is really spongy. Therefore, we bled the brakes again, still spongy. Here is where it gets weird; when the car is off I get a full brake pedal but as soon as I turn the car on I lose that pedal almost entirely. We checked the vacuum lines to the booster and they were fine, but for the sake of knocking off possibilities we replaced the power booster. After a few hundred dollars later my pedal is till really low and spongy, If you disconnect the brake booster through the vacuum line it gives me a full pedal but as soon as you hook it back up I lose that pedal. For reference, I have no leaks in the lines because I check the fluid all the time and I never lose any. I really need help because I can't figure out with to do to regain my brake pedal, I've tried everything....