Glenn,
The racefit goes directly from can via welded link pipe onto the back of the cat's under bellypan, it's a slip on fitting, doesn't have banjo clip, just retaining spring and some sealant on the tube faces. Racefit can just has basic silencing packing inside.
The orginal end can has cat's in it , plus exhaust valve, the big squarish box after end can is just empty and I guess purely a back box for silencing.
the two underbelly cat's and lambda sensors are still there. Unfortunately they are welded to headers. The 06 I believe had these cat's bolted in place, so you could remove and use a Cat replacement pipe such as from Motad. Jon at racefit reckoned there wasn't a lot more power to be had by removing the underbelly cat's. I don't know I am not an expert. I would have thought maybe another 4 hp or so. He said if I was interested, it could be discussed about decating them or fabrication of replacement pipe. Not really sure at the moment, you would need to have taps made up I guess for the lambda sensors or run into problems with the FI. Also it maybe possible if the pipe bore is the same as Racefit, to use header assemblies from Akra or Micro that you sometimes see come up on ebay for older generation bikes.
There are a few guys with Growlers on the site, I wonder if any of them have done any dyno work for maps already or are running PC3 with it. I may go down that route, it's early days.
cheers
John