It may not translate to your application fully, but from what I've heard about the Motordyne XYZ pipe, the resonator option is slightly quieter than the HFC option and doesn't add any restriction vs a straight pipe. So removing the resonator and adding an HFC section probably won't make it any quieter than it already is if loudness is your main concern, unless you go for something really high cell count, which would be pretty restrictive.
Another possibility is getting a resonated Y-pipe. Off the top of my head, I know Motordyne and Litespeed both offer them. Motordyne's section can be switched for straight piped or HFC, and Litespeed offers in both SS and Ti.
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