lots of check valves, metering valves and residual valves in lotsa places in modern brake systems---they can be check/residual valves in the master cylinder, in the combonation metering valve you will find portioning , check and meter valve pieces and of course if your master cylinder isn't returning all the way your brakes will drag and most times probably the fronts as more pressure is sent to the front so if the master doesn't return you will have a lot of drag---

In your case----just what parts do you have on the car, and how are they plumbed????

Also did you bench bleed the master???