I'm not sure I follow how it would be, but thats interesting if it is so..
We have to run with catalysts in our saloon race series at castle combe in 2009 so may be worth considering this

We have a 340bhp 1.8T Audi TT and for the odd trackdays are forced to run extra silencing which we do in the form of a tailpipe muffler as it is easy to fit and remove -



http://www.merlinmotorsport.co.uk/p1...duct_info.html

we have a 3" exhaust and this muffler is approx 2" clear I/D and the 8" long - this makes a distinct reduction in power delivery, so I'm interested to know how much effect a Cat would have, even a 100CSI one. If there is benefit in fitting it at the back then that's what I'll try.