MUFFLER OPINIONS

changeing the position of the muffler i.e length of pipe between it and the exhaust port can have a dramatic impact on drone or at least the rpm it drones at.

another option is a small resonator box some way after the collectcor ends i.e more than about 8 inches further back, and before the muffler, takes the Crack out of the noise and alters the rpm it drones at.

the drone is due to a standing wave. dicated by RPM and length of pipe before muffler when multiples of the standing wave, wavelength perfeclty fits, into the distance from the exhaust valve to the opening into the muffler, at an rpm you sit at when on the freeway. Then the drone gets you down. if you change it so it does it a different rpm you are usually too busy hanging on for dear life to notice or its a problem a few seconds as you acelerate away through that rpm.

you go some way to achive a similar outcome with an X or H pipe in a 2 outlet system.
that junction acts as a disruptor to the standing wave and alters where the resonance is

Dave