I have an 8.8 with disk brakes in my 89 renix. I recently put in a wj brake booster. The write up i followed shows to pull the pin out of the stock proportioning valve and remove the rubber o-ring from it. This was supposed to accomodate the rear disk brakes. Well my rear brakes really lock up fast now. What is the best way to fix this? Where can i get another one of those tapered o rings that come of of the stock prop valve? I have searched and have not had much luck. Thanks in advance.