Ok I need some advice. I'm so pissed off right now.

So latest events that have happened over the past couple months (mentioned some of this already in my previous posts):

1) Dropped the car off about a month ago and reproduced the problem for one of the mechanics. Left the car there overnight. Get a call the next day saying they reset the drive adaption values and the problem went away. Got pissed off and told them that's been done twice already the problem comes back everytime. Was told to file a case with BMWNA. Did that - they get back to me and say they can't do anything because the dealership told them they weren't able to reproduce the problem (f'ing lie). Pick up the car while the office was closed one night so I couldn't talk to anyone. On the drive home, SAME DAMN PROBLEM HAPPENS.

2) Called the next day to complain to the SA. She told me to bring in the car again. Had to go out of the country on vacation so I told her I'd bring it in a couple weeks.

Now for the recent update:

3) While driving the car to the dealer on Tuesday, freaking thing overheats. I wasn't able to drive the car for them to reproduce the problem as a result. (they had to change the water pump and I couldn't stick around) SA tells me not to worry, she's sure they will reproduce it on their own. I leave. Get a call that night saying the mechanic said the problem is THE BATTERY. The battery is getting weak and [fill in some b.s. excuse here] is causing the rough downshift. After the charge, they tested the car and the problem was gone.

4) Go the next day to pick it up. With the same brainiac mechanic in the car, take it for a spin. Well what do you know - problem is still there. Now the mechanic goes from saying it was fixed and caused by the weak battery, to saying this is NORMAL. Go back to the dealership, tell them if it's "NORMAL" let me drive another 2009 X5 to see if I can reproduce the problem. They put me in one, same year, MORE miles - and guess what - NO PROBLEM. I come back after the drive, tell the service advisor. She calls the foreman over. Foreman gives some b.s. excuse that because they didn't reset the adaption values in the other car first, I wasn't comparing apples to apples. I tell him to reset them and I'll drive it again - he says - "that isn't necessary". We go on the drive.. reproduce the problem for him - he says "he's felt this thousands of time" and it's a "software issue". Then he says they need to get BMW Engineering involved and that I'll hear from them shortly.

5) Get a call today. They said BMW Engineering said this is NORMAL also. It's related to the Idle Control something something b.s. I re-iterate - if this is NORMAL why doesn't it happen on the other car. "Oh I guess it's just more prevalent in your vehicle". I told her I'm coming in tomorrow and I want to talk to her manager.

/end rant

Hopefully some of you guys made it through all that and can provide me some advice. I am definitely going to push for them to reset the adapation values on the other car and let me test drive it. I'm sure the problem still won't be there. From that point who knows what they will say - I'm guessing something along the lines of what they said earlier - "oh I guess it's just more noticeable in yours".

What should I do? Threaten to contact the BBB? Take them to court? I feel like I'm running out of options here.

Any advice would be appreciated.

EDIT: I should probably mention, the car is under CPO and it expires in February of next year. I'm sure if the car wasn't under warranty they would've replaced the tranny the first time I took it in.