Thanks! If I understand, your purpose for the resonator after the muffler is sound control. Seems to me it's too far downstream to have much effect on scavenging. I may be wrong about that.
Indeed the resonator is there to control sound. It is unclear at this point how effective that chamber is in the current configuration . . . the system exhibits quite a bit of Rap under acceleration. I may choose to add a mesh cone at the end of the chamber or a mesh spiral through entire length (or both) for some additional quieting . . . the space is provisioned.
As for how far downstream 'scavenging' can be promoted . . . this remains open for debate. With head-pipes feeding into equal sized steel-pack muffler cores in turn dumping into smaller mid-tail pipes - exhaust gas velocity is maintained. The system as whole is designed to produce a vacuum at the exhaust ports.
