Hydroboost issue

I have had that problem before and it took me a long time to figure out what is was. It was the brake line itself that runs right into the caliper. What happens is overtime that rubber line breaks down on the inside and when you push the piston back into the caliper to put your brakes back on it forces that fluid in a upward direction which is opposite from what it normally does and it cause the rubber on the inside to fold up. Then you have less pressure going to one of your calipers causing the car to pull to the opposite side that you have the problem on. I hope this helps.