Brake Squeaking Noise problems of the 2005 BMW 645

My car a 645ci 2005 started making a squeaking noise and I replaced the brakes and disc after spending $800 my car was having the same problem. I run the machine and said that it was the brake booster. I took my car to my local mechanic and bought a compatible piece for this car and got worse. Then after spending over $400 I realized that there was a recall for these piece where BMW my local dealer in NY wanted to charged $2500 for the job. I tol them about my local mechanic and they would not touch the car because the original piece was removed. What cn I do I had to drive over 20 miles back to my house without brakes I was using my emergency brake the whole trip.