Hi Jim
I just put a TSL 'Thundercat' Sports cat on my type R and got a remap.
Great result from it over the standard downpipe.
Andy Forrest asked what exhaust system i had on the car and seemed impressed with the result he got from the map.
Just make sure you get downpipe with a bell mouth, allows much better gas flow from the turbo and waste gate without interfearing with each other. And make sure you buy a 100cel cat as its less restrictive than a 200cel.
Hayward and scott do a sports cat and say it produces only 2bhp less than a full decat, but costs approx £525.
The TSL offers gains of approx 20bhp over the standard pipe so is also approaching the flow of a decat pipe at a cost of £395.
You can get a bellmouth sports cat for around the £250 mark though.