you do know that when they "inspect" the sub frame all they do is put it on a lift and look at it with a flashlight and say...yep its good when in fact the only way to tell is to take the entire sub frame off of the car which is about a 9 hour job and buffing all of the mounting points to see if there are any cracks where the sub frame bolts to the car, which is hidden by the bushings and everything attached. the only thing they will see is if its severe enough to have spread a good amount. its almost guaranteed that most people on this forum have slight cracks where their sub frame mounts. because of this i just purchased the turnermotorsport reinforcement kit to have them weld in when they change the sub frame bushings with power flex bushings.
the dealership isnt there to help you its there to waste your time and take your money, for instance when i was accelerating i heard a huge bang then the back of my car started bumping up and down and banging when i accelerated. took it to fields bmw in orlando since i was about a mile away, had to pay a mandatory fee for them to look at it since it was towed in, they said it was the differential. well 2 days later when i drove back down to orlando to get my college books out of the car since i forgot them and i saw the car sitting in the exact same spot as it was when the tow truck dropped it off. i told them they were full of sh!t and the car wasnt even looked at because i saw how it was parked with the back left tire on the line in the parking spot and the wheels were turned all the way to the left the same way it was parked when it got dropped off. I told them i want a second opinion and had it towed to PSI about a mile down the road, they looked at it and found out the guibo, and the centerline bearing on the driveshaft were shot along with the bushings on my diff, the diff itself was perfectly fine. i raised hell with bmw and finally got my money back after threatening to sue them if they didnt refund the money.
ever since then i will never trust the stealerships except the one close to me since my friend is a mechanic there and i request him to do all the work and diagnostics.