Hi Bob

Amazing as it may seem I weighed the Rossi 40 with the tuned (black) muffler and the TT40 with the stock muffler and the weights were within a 1/4 oz. The Rossi the heavier. I also compared RPMs on a apc 9/6 prop and of course the Rossi had the TT40 by about a 800 to 1000 rpm. But with a perf specialties tunned muffler the TT40 matched the Rossi on the ground. I don't know about air. Of course the TT40 with PS muffler costs more than the Rossi with tunned muffler. I've been running the Rossi 40 and 53 on 3D planes and they are well worth the money

Denis