sx can question

Everyone says that a can on an srx can rob you 5hp. Does this apply to the cans for the non power valves motors as well. I was thniking of putting one on my 600sx, but I don't want to waste my money. Any help on this would be great.
Thanks

I had one on a 99 700 SX. Seemed to be snappier out of the hole. I heard in Wis or Min they will give you a ticket if you have done any altering on the exhaust??? I haven't got one yet but it's always in the back of my mind.