just got the W258 inserts from DK custom, only took a few minutes to install, its late here and frikkin cold so i only went for a very short test ride but i like the sound of them. the 3'' mufflers without baffles were just stupid loud and missing any semblance of back pressure. these toned em down to a still friends with neighbors level plus i definitely gained some back pressure.
i will know more when i take the bike to work tomorrow as it is an hour one way so i can give more details then.
i bought a few things from them now and i gotta say i am very happy with the service and the products so far. they accidentally sent the wrong item once and kevin went out of his way to make it right...on a holiday no less. considering shipping probably cost more than the item purchased im sure he lost money on this one (i am in canada)
customer service like that is hard to find so they earned my respect and my thanks....not in my nature to sing praises but they earned it this time.
well after having the inserts in my bike for a while i can say i do like the sound of them at idle, i know you cant hear the person on the other end of the cell phone when i get on the throttle to pass and at certain rpm/speeds i really like the sound the pipes make when i shift.
the performance has greatly improved compared to running without baffles and i did gain some mileage back as running without baffles seems to suck the gas right out of the tank.... i went on a long group ride with a handfull of friends (10 hour round trip) and was getting crazy good mileage on the run like about 80 km or so more per tank than what i usually get and thats with most of us hammering on it every time we came to a stop :-)
machinistmate is right you will need to open up the stock hole so the inserts can be bolted in.
if for some reason the stock bolt/screw/rivet wont hold the baffle in after you take the inserts out (if you ever do) it is a simple easy and cheap fix....just upsize the fastener :-)
I would love to add a sound clip of my exhaust but it will have to wait for a day off AND the weather needs to cooperate. keep in mind my set up may sound different than yours as i have the stock mufflers on my bike an those puppies are 3 inchers :-)