My right front and left rear calipers aren't bitting as hard as the others. Take into mind that the brake lines are criss-crossed from the prop valve(which is normal).Could this uneven brake pad wear be from a faulty m/c or from frozen calipers. Setup: gsr brakes all around on a 97 hatch with new brake pads.

 

I would bet that a fauly MC would give you more of an air in the brakes feel. Possibly a bad prop valve though.

 

Or one further a dying caliper as well.

If not that I'd move up the line to the prop valve for sure

After that then check the m/c. But odds are the m/c would cause a weak/mushy pedal feel, almost like no pressure.

 

I have a MC and porpotioning valve from a 2000 si if you do decide to replace it