My L9H non-AFM Sierra slaps pretty good when it's cold. It's bad enough that my 17 year-old daughter noticed in when she drove away one morning without letting it warm up. She calls me up and says, "I think something's wrong with the truck. It sounds like a diesel." I then proceeded to explain piston slap and tolerances.

It has 70k miles, does not use one drop of oil between changes, and quiets down after a few minutes. Remote start is great because we just start it five minutes (or more) before we plan to leave. I'm not worried about it. That truck and engine will probably outlive me.