My brakes suck. I have a '93 XJ on 34's with the stock 30 front and rear disks from a ZJ on an 8.25. I removed the o-ring in the proportioning valve when I installed the rear disks. Last week I swapped in a master cyliner from a one ton E-350 and now my brakes suck slightly more. What should I try next? I was thinking about swapping in a dual diaphram booster and going back to a smaller MC which would increase line pressure but after pricing parts I'm considering other alternatives to imporve braking performance. What exactly would removing the proportioning vavle accomplish if anything? What does it do beside bias braking front/rear?