right, thats why i asked if he thought every misfire would cause a large enough change in RPM to dictate a misfire CODE.
i work on a TON of GM trucks/suv's with the LS motors. notorious for vacuum leaks at the intake gaskets, and will show constant misfires at idle on any scanner, but will never set a code. thats all i'm saying is there is always instances of problems that dont set a code, even misfires. however that might not be true with the 5.0 as i have no experience with it yet.
i'm not arguing that his car is misfiring or not, i'm simply saying no code doesnt mean no problem on ANY vehicle.
Also keep in mind the TiVCT/cam profiles also makes these cars sound a little rough and lopey at idle. Nothing near a performance cam though.