I am looking at adding a little performance boost to my 2015.5 V60 R-Design T6 Polestar. I wanna have a little fun with this car without breaking the bank or the car. I am currently looking at the Ferrita cat-back exhaust system and the TDI CRDT4 MULIT+ RPM tune box. Does anyone have experience with these components? Do they actually work to improve performance? Do they hurt fuel economy? Is the exhaust going to cause droning on the highway? Has anyone had experience with a dealer giving you grief about having these on your car? I haven't been to a dealer here in Indiana yet. I just got the car back in December and it hasn't needed maintenance. I'm about half way between the dealer in Indy (Tom Wood) and the dealer in Bloomington (Volvo of Bloomington); any recommendations? I appreciate any feedback you all can provide.