Replaced the front pads last night, and then flushed the system with new fluid....well, all of the system but the two rears. I couldn't get either of them to budge, even after PB Blaster. I vacuum bleed the LSPV and the two front and MAN was the old fluid toasted!! Ok, here is the question. The brakes feel very spongy. And the stopping power just isn't there. Do you think: 1) air in ths system and I should do the normal 2 man bleed 2) toasted rear fluid that I couldn't flush is the culpret 3) something I am not thinking of I replaced the rear pads about 6 months ago, so I know they are good. What Cha Think?