I was very interested on the Aero muffler, but after asking the question in this forum I changed my mind. It included a special air filter and the muffler which they were selling at the FMCA rally in Indio, CA a couple of years back. It saved me around $1200.00
Actually all my coach needed was to change air filters from the original which was a Farr to a Racor. As soon as I changed filters my coach has a lot more power going up long steep grades. With the original Farr and the Wix later on the vacuum gauge would go right up like if the filters were plugged up even when new. With the Racor the vacuum gauge works perfect below the condemning line.