mmotown

Guys I am not under warranty. My car has 139k miles on it. I have noticed when I start my car there is a ticking....clicking but it is controlled by idling or acceleration. Over the course of time it has gotten louder. What could this be? Timing chain? Which the dealer ship fixed when my car was under warranty or a manifold leak, and what is this I hear about the heat shield? Thanks guys for your input