Thanks for the tip on the Riordan Turbo resonator. We've had the resonator fail, alternator ($1,100 for part alone), leaking fuel fittings, failed idler pulleys (2),transmission leak, two failed A/C/heat blower switches, brake pad warning sensor, EGR valve, even the antenna fell off ($200 for part). This vehicle is parked under cover each night, and has 54,000 miles. I realize the OP wasn't looking for opinions on Sprinters, but I just cringe thinking someone is considering buying another one. Here in the Atlanta area, biggest problem is dealers. They are mostly concerned with getting you a manicure, or a massage, or signing you up for yoga or hitting balls on their driving range, or tasting their gourmet coffee-anything but fixing your vehicle. You can only talk to your service advisor at a scheduled appointment, and don't even think of talking to a technician! OK, thru ranting. I predict that three years from now virtually every class B and B plus that's on a Sprinter chassis now will be on a Transit chassis, and you'll be able to get them worked on at every town in America.
My daughter has a mobile grooming van built on a 2006 Sprinter 2500. It is similar to an RV in that it has fresh water tank, gray water tank, 2500 watt invertor, shore batteries (six 6 volt), two water pumps, plumbing, electrical etc. While we have it mostly sorted out, it has been the most unreliable and expensive vehicle to service that I have ever owned. I just purchased a 2016 Pleasure Way Lexor TS. I did not consider any class B built on a Sprinter chassis. It sounds like you are thinking of buying a new class B? If you don't like the RAM Promaster, why not wait until a class B you like is built on a Ford Transit? For every other type of conversion, they are rapidly overtaking Mercedes in sales. I believe it would prove to be considerably more trouble free, and far easier and less expensive to maintain. JMHO.