If you do not have the Dinan stage 2 tune and drive with it daily, its difficult to take you seriously on downing its performance or Dinan's backing of their product.
I had mine done at Motor Works West... but here are the many dealerships within 50 miles of Edgewater, NJ. (where I live) that sell, support and ENCOURAGE Dinan products and tunes.
For me, PPK wasn't an option since I don't have the 335is, the dealer won't install it. 3 different dealers all suggested Dinan (even the non-dinan dealerships)
If the tune causes any issues with the car that the dealership determines was because of the tune... the dealership contacts Dinan and they cut a check. It's only happened a handful of times from what I was told from the Dinan rep. The warranty is what you are paying a premium for. And for some, it is worth it. Me being one of them.
2011 M3 E93