Clown Shoe Motorsports is located in NW Dallas. One of the two owners/techs is Phil Fromme and he has well over 20 years experience with German cars (also a Porsche master tech) - have known him for decades. I'm not sure what his workload is right now, or what the cost would be, but you might consider calling to check.
The website makes it seem that he and his partner are "BMW only", but that is not the case.
Clown Shoe Motorsports