I would NOT get service from a dealership in the Nashville area if you have ANY aftermarket parts installed. If you plan on installing aftermarket parts remove them before any service at the dealership.
That said, Nelson Mazda, 2 locations in Nashville (Hickory Hollow & Rivergate) are both Mazdaspeed dealerships.
My experience with both has been eye opening. I bought my MS6 at the Hickory Hollow location.
I ordered the Mazdaspeed CAI thru the dealerships parts department and the service manager tried 'unsuccessfully' to void my warranty. The service manager backed off only after I had the Sales manager & parts manager talk to them.
Tried the Rivergate dealership (same owner as the Hickory Hollow dealership). I took 'her' in for one of the original ECU recalls if I recall correctly. Anyway, I did not remove the CP-E TBE and the mechanic called the service manager and then ME back to talk. They didn't wanna do the service/recall item that I had come in for but after 30 minutes of arguing, they reluctantly did the service I requested but only after making me aware of the fact that they would be making the appropriate NOTATIONS in their service computers about the modifications I made to the car/vin number.
I have since found a very good mechanic/tuner/car enthusiest to perform any an all service, I may need in the future. As I believe my warranty is shot.