A few years ago I got my 68 Charger resto mod on the road. It had manual drums. I converted it to power/front discs. Because of the cam I have low vacuum so the brakes are marginal. After several suggestions from other Mopar friends I installed a vacuum pump. I now have plenty of vacuum at the power booster but the braking hasn't changed. now when I step on the brakes I get a loud Groan from the brake system. (I have a video, too bad I can't play it) It sounds like it's coming from the proportioning valve. I have bled the brakes several times so I can't imagine any air in the system. Any ideas?