I recorded some sound clips to show how resonators help/change the sound.
Comparison of ISR y pipe, Z1 resonated y pipe, and Henko dual resonated y pipe
Exhaust setup is Z1 headers, Circuit Werks non-resonated test pipes, and ISR single exit

ISR y-pipe

Z1 resonated y-pipe

Henko Autolad udal resonated y-pipe

 

I put the videos together to make it easier to compare.

 

Think I liked the Z1 the best. Interesting test though. Would have been curious to hear how resonated tp sounded given the other 2 options both included resonators