A long time ago a TTR owner chopped up his standard exhaust and removed various bits of internal metalwork and welded it back together again. He kindly did some drawings (in the days before everyone had digi-pic capability!) and I put an entry and links to the drawings on the FAQ.
However, I had several owners feed back that the modifications made the exhaust sound loud and raucous and didn't seem to help with any extra power.
Beraing in mind that sound sensitivity exists in more places than just the UK, and the mod did little to gain power, I deleted the item and now can't find the diagram or notes.
There certainly isn't a cat in there but it IS very heavy.
I have a spare CRD silencer here that you are welcome to try if you like?
The benefits of the CRD are the same for most after-market silencers in that they weigh a lot less than the standard box and, as the weight is quite high up on the bike, it does make it easier to pick up off the deck
They are usually flow more freely than the standard box and give extra power.
They are usually in chrome, polished alloy or stainless steel and look a lot nicer than the standard box.
The downside is that the after market jobbies are, to one degree or another, invariably louder than the standard one. If you ride in sensitive areas (and that seems to be most of the UK!) it is an issue that shouldn't be overlooked.
CRD pipes can be quite loud but can be modified with inserts to be quieter.