LOL It actually went with three exhaust OEM, ZD and the limited edition Foxtrot Oscar one. Dave had only driven his car a short distance without exercising the full rev range and thus only experience the Jekyll aspect of the Zero Drone , not the Mr. Hyde as in this video by James:
http://www.youtube.com/watch?v=yxXou5GWKoc
Then he installed the FO exhaust and boy was he surprised, I think I heard him here in Cardiff lol!
I think Dave will be going back to the Zero Drone shortly.
but might release Mr Hyde more often.
As for the dual canister type...I had those in my 1979 Mustang back in the 80s, they are just a one trick pony IMHO.