"New" (to me) vehicle that we took out for a maiden voyage. 1956 Chevy 210 with upgraded power brakes. Was hearing a "whistle" sound when driving but not under power that would go away when the brakes were applied. I also noticed a rough idle that lead me to believe I had developed a vacuum leak in the brake system. On the way home, the brakes started dragging to the point that I had to pull over and ended up towing the car home, although the brakes released by the time we got the trailer there. I was thinking it might be the seal between the booster and master cylinder but found that the booster check valve grommet was torn. I'll get a replacement today and hopefully this will solve my issue. My question, could a small vacuum leak cause pressure to not release from the brakes (lock up)?? Or is there something else I need to look at? Thanks!!