ticking noise in 2008 4.8 silverado

so i notice a ticking noise coming from number 7 header tube it goes away when engine is warm at idle but you can hear it when you give it gas going down the road not really loud but is noticeable. is starting to scare me a little bit. I was thinking it was the header gasket or a lifter anyone has any ideas?

check rocker arms

Sounds like piston slap. I wouldn't be too worried. I remember hearing something about the 4.8L around that year having issues.