So I have replaced 3 frozen calipers with used ones from another car. After bleeding the system I went to throughly test them out. I did 4 rubber burning stops from 75mph and some fairly serious braking from ~35mph. Finally on th way home the pedal went ALMOST to the floor. There was still some braking left (perhaps the booster was failing?). When I got home I checked the brake fluid and it had boiled over. I have heard that the brakes and vacuum system are linked but I do not know how. Following this I have had some vacuum system issues. The fuel shutoff is not doing its job and the drivers door doesnt close properly. It was fairly damp last night and perhaps that caused the fuel shutoff/door issues? Is the boilover normal followed by loss of some braking? I know I should have replaced the calipers in pairs with 4 new (reman oem whatever) ones but money is tight. I purposely tried to get the brakes to overheat and braking was excellent until the loss.