Brake Issue

[gabedrummin]

So a little history 2000 Boxster S brakes are about three years replaced rotors and pads .I do a brake flush every year.
Driving home from work a couple of weeks ago the rear brakes develop some issue . I'm on the free way doing 80 ish within a few miles I pull off because I feel the cars brakes dragging . Both rotors are blue they got so hot the brakes were locked up. I get the car home and try to bleed some fluid off .No way I cant get any fluid through the system by pressing the brake peddle. I have replace both rear calipers and rotors and pads .Put in a new master cylinder .Vacuum bleed the system at all 4 corners . I go for a test drive and passenger rear rotor is noticeably hotter than driver side .Assume I got a bad caliper .exchange it for another do another bleed and same issue . I have checked the parking brake and its not the problem .S.O.S. Cant afford to take to dealer. I'm at a loss and would really appreciate some of your thoughts as to what the problem could be .Thank you guys .JEFFPA What do you think?