Knock on wood...the beast has returned home and seems to be working well; Assuming everyone has been forthright, the problem was the Throttle Actuator Bank 2, which was the original fault code we got before the reflash that gave us different codes. IMO my dealer did the best he could with what BMW NA was telling him to do. This forum was very helpful because I actually sent an email to my dealer before he replaced the DSC telling him that the Throttle Actuator was a previously known cause of "DSC Malfunction" errors...it made it difficult for them to try to charge me for the Throttle Actuator.
Saga;
1. DSC Malfunction, limp mode, etc..
2. Computer reflash. BMW opens PUMA case with direct corporate involvement.
3. Dealer replaces DSC/ABS Module for $1950.53. 7 weeks downtime. Same DSC Malfunction re-occurs at dealer's shop.
4. Dealer goes back and forth for about one week with BMW NA to re-diagnose and get the Throttle Actuator 'goodwilled' ($2100). I'm supposed to be thankful.
5. Dealer replaces Throttle Actuator Bank 2 and says car is fixed.
6. I drive car for 30 minutes and get same DSC Malfunction.
7. Dealer says they "didn't plug in a wire correctly on the Throttle Actuator" and kept car for another week. 10 weeks total downtime.
My lesson learned is that BMW has a poor diagnosis system but retains total control over parts and diagnosis so the end user has no recourse. You can read these misdiagnosis' all over this Forum. When they don't know the exact problem they have to quote you the $2000 repair and all along it could have been a $463 repair. We get an expensive new part that we never needed and a lot of downtime. If overpaying-without-recourse bothers you then I highly recommend staying close to the dealers; emailing dealer regularly with forum-suggestions and for status updates, and going by after they have installed parts and see if the replaced part was the problem. And with PUMA cases it doesn't help to get a 'second opinion' because BMW NA just gives the second dealer the same recommendations.
Thanks again for everyone's help!