You need an actual muffler to get an sound reduction out of your current setup. I would put in a Magnaflow 11366 muffler on the passenger side (stock location of muffler) and run no resonators. Should be nice and light still.
Different setup here, as I'm running the stock header and cat, but just for a point of reference, I will be building my new exhaust system this weekend with the goals of something that's tolerable on the street and at the same time drops a few pounds vs. the stock system (oh yeah, I hope it flows well too).
I am using the 11366 magnaflow muffler that Dinan604 mentions where the RH stock muffler went, exiting thru a Cooper lower valance with a 12512300 Hushpower as a resonator right behind the factory flange. I will report back how well it turns out.
In the past I ran the regular Magnaflow cat back system, eventually melting the insides of the resonator and replacing with a straight pipe. Both with and without the resonator were a bit much for my ears on the highway and non-gearhead passengers were less than impressed. I'm hoping the hushpower / magnaflow combo works a little better.
That should be quiet enough to pass tech. I run the DINAN muffler with no resonators and there's no drone.
There's a youtube clip of someone with that muffler with zero resonators, but larger piping. A bit droning due to the increased volume, but not too bad.
[ame=http://www.youtube.com/watch?v=hXr6ko6wmT4]YouTube - Magnaflow custom exhaust Mini Cooper S R53 sound[/ame]
Well, I finished up the custom exhaust this weekend, using the hushpower and magnaflow as I mentioned above. It maybe under the SCCA sound limit, but the interior resonance is much worse than even the standard MINI Magnaflow cat back with resonator delete. Not much fun on the street even driven gingerly. This is probably not the best option out there!
I ended up with only a "turbo style" (don't know the exact part number) magnaflow muffler. The sound is much, much better, even without the cat. I haven't tested it for freeway drone yet, but if it's that bad, the cat will go back in. Overall, I saved 20lbs off the RMW flowmaster back end that was on the car before, which was already lighter than the JCW system. I'll post pics if I get the chance..
