I just received my UDP in the mail, and I was opening and saw a warning on the box that said "AFX pulleys are not intended for highway. AFX Pulleys are for off highway use only." Now I've read that no one has had any problems with these pulleys before, but I was just wondering what the warning was all about then. Why would these pulleys be bad for highway use? Any thoughts would be appreciated.

That's a legal disclaimer, means it's a part intended to increase the power output of the vehicle beyond it's original intent. That way if you get busted for racing or whatever you can't say "Well, I didn't know what that part was"

trust me a cop ain't gonna go look in your engine bay and go hey whats that shiny thing in the back of your engine, doesn't look stock. haha