Considering buying an exhaust system for RS6 C7 2017 and have a few questions: 1) Is it true that an Akrapovic system will not void the Audi warranty? 2) I have been quoted £7400 for supply and fitment of the Akrapovic cat back system, anyone had cheaper? 3) Will a Milltek exhaust system void a warranty? 4) If Akrapovic system does not void warranty, does Audi have to fit it? Thanks in advance.