i think your friend had a little to much miller before he made that statment, exhaust vavle has to be closed in order for the cylinder to make it's compression cycle, i think he's just jealous cause he wish's he had bought the r6
I read that somewhere. Something about a valve in the exhaust which closes towards the top end of the rpm band due to noise regulations? Doing the mod keeps the high rpm hp from dropping off. Not sure if it is only at that rpm range or all rpm range and as others have pointed out, open all the time would ruin the lower rpm hp/tq.
This is just off the top of my head, someone will find the link and throw it up. Those cheaters have some pretty nice street torque down low and they growl too. Still not a fan, but wouldn't kick her out of bed either...
It's a valid mod. My friend has it done to his. It doesn't keep the valve open all the time. Just on a certain RPM up to redline. U.S. bikes open then close the valve variably. It opens to create more mid range and closes at the higher RPMs for noise regulations. Basically this mod make's US spec 636 bikes act like Euro counterparts. This is all from my friend's mouth. Please don't flame me if I'm wrong.