I just installed a magnaflow cat back on my 05. I didn't notice it last night but today I fired up the truck to listen to the exhaust again and I hear a ticking type sound. It is definately coming from the exhaust. Could it be an exhaust leak?

You can hear it here:

 

Sounds like somethings loose. Go under the truck and see if any clamps arent tightened 100%. Do this when the truck is on. If they are all tight, check all the welds in the factory piping and see if you cant hear any air coming from any of the welds.

 

It isn't an exhaust leak because it would be more of a hissing sound only near the joint of the leak. There may be something inside the exhaust like a mesh flare or something disrupting the tone. A part of honeycomb in the cats may have cracked.