(I posted this in Engine/Fuel/Intake/Exhaust, then realized it would be more appropriate here):

After a bunch of reading here on HDF regarding the V&H QBs, I gotthem for my '07 FLSTSC w/V&H Fishtail II slip-on mufflers. They now sound almost exactly like the Samson Silver Bullet fishtails I had on my '97 FLSTS (which is a good thing...I always thought they sounded great.) With the stock baffles, the V&Hs sounded kind of like a drag bike...too much high-pitched "clatter". The quiet baffles attenuate the higher sounds and leave the rumble. My wrench said they probably wouldn't require another re-map, and it runs fine (I was getting some popping on upshifts, which is now gone.)

 

Put them in my Pythons and had the same results......for about a month (@2200miles), and then some of the sounds of the stock baffels came back, I describe it as a bird chirping sound. Not really bad but it is there and very noticable when passing a large vehicle on the highway or going by the jersey barriers. It comes mostly under throttle, once I settle in at a speed it goes away. The sound is still a little quieter and is still deeper that with the stock baffles. I think some of the fiberglass wraping has worn out already.

I still like them a lot and many have commented on how they like the deeper sound a lot better.