2000 Chevy Malibu ticking noise

Take a rubber mallot and tap on the catylatic converter. THere is a chance internally it is loose. If that isn't it, an exhaust leak can ofen cause a ticking sound, but that usually goes away when they get hot.

Let me know what you find. Also, make sure the resinator isn't ratteling inside. If I recall, it comes after the muffler which may be why it went away with the old muffler and the new one is forcing enough pressure through it again.

Joe