pvanbeveren

Hello, i have a 2002 A4 quattro 1.8L 5 sp with about 150k miles. the front left brake won't release meaning it constantly is applying pressure to the rotor. I have replaced the caliper, master cylinder, and brake lines and it is still doing it. I can bleed the brakes and it helps for about 15 - 50 miles. At this point i am at a loss... Any ideas would be greatly appreciated...I have replaced the pads twice now due to this problem and i am not able to shift out of 4th gear if i want to maintain my speed... HELP!!!