I was pretty happy with the Moroso muffer at first.  Only 3 lbs, sleek, sturdy, good looking, and toned things down perfectly.  But because I never really rage around at full power, I didn't realize how much power it was costing me.  Coming home from Vans homecoming I flew with a couple guys with 180hp c/s props and was sad to discover that I just couldnt keep up... gadas!  I fugured it might be the new muffler, so I did a couple of test runs at WOT (number from my guages - a little faster than actual):

                     moroso spiral             No Muffler         Fuel flow matched (throttled back some)
D Alt                 9200                         9400                  9400
IAS                   148kts                      159kts               151kts
TAS                  168kts                      183kts               172kts
RPM                 5600                         5950                  5700
MP                   27.2                          30.3                   26.9
Fuel Flow          12gph                       15.5gph              12gph

Obviously, that muffler will fly never again. Sure is good to have my power back.  Maybe the hollowed out flowmaster will be back some day...  But it is kinda heavy...

Note, I am still a little slower than with the wastegate closed and 2-bladed prop...  but close enough.
--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net