I have the CP-E downpipe and a custom cat back installed on my 6. Fair enough if you want to wait for the warranty before putting in a downpipe as it may give you the typical turbo seal problems a lot of people seem to have (I have not experienced in mine...yet) I thought the standard 'Y' piece was a more like a curved 'T' piece and I felt it was a bit restrictive too. As Russell mentioned above the corksport exhaust is an option and a better flowing exhaust gas design. I opted to get a custom cat-back designed, fabricated and installed when I had the downpipe installed. Labour was all done in one hit to save me time, cash and hassle.
I can't comment too much about the standard mufflers being restrictive, but as a short answer I would say 'yes they are' IMO. The mufflers I have which are Super-cats are more of a straight through muffler, which, by rights, should deliver a better flow, thus additional performance. The amount of gains (if any at all) in comparison to the stock mufflers I honestly do not know, but that's just a personal opinion really. I've always thought the quieter the exhaust the harder it is for the exhaust gases to flow out, (being muffled).
In regards to exhaust note, it really depends on the individual really. Personally I'm not really a fan of a super quiet car. They're boring to drive, and does not really give you the passion of driving a sports car. In saying that, milo tin exhausts are annoying, loud, cheap and have 'hoon' labelled all over it. In conjuction with my two supercat mufflers I have 3" mandrel bend coated mild steel piping, one resonator located just after the DP, a second resonator located further down, which then split into the 'y' piece and into the two mufflers respectively.
http://i196.photobucket.com/albums/a...6/DSC00210.jpg
http://i196.photobucket.com/albums/a...6/DSC00209.jpg
The result (based on my set-up) is;
- A 'beast' on cold start-up (2,000RPM)
- Very quiet on warm idle.
- Sound and performance under throttle,
- Very quiet in the high gears cruising.
- At one point I was getting about as much road noise at 100kmph than I was exhaust note.
If you find yourself attending a cruise (WA) or meet and I'm there I'll show you mine. Toddy also has a similar exhaust but was designed by another chap. His is a little more louder than mine. Hope that give you some idea. If you have any questions about the above let me know