Installed a FRPP resonator delete x pipe on my 2015 GT A6 and got a little change in sound and then decided to go with a MBRP Cat back Street version with H-Pipe .First of all I must say that this piece is a work of art excellent quality and finish and I love the 4.5'' tailpipes.Installation was a snap Nice deep sound no drone on the highway and gotta love those A6 sport mode downshifts.