Your car must have had some tweaking to still be pulling that high up,what spec is it?
Well TBH all i can tell you is it had an ECU chip fitted back in 2005 i only know this as i have a recipte in the paper work i got with the car, i phonned the company who did it and he told me after a bit of a chat that it would have been up to 195 bhp.
I have fitted a Milltek cat back system, but i have never had it on the R/R, i will do though one day soon