Idler pulley #2 rattle

So over the past few days I've noticed a horrible cracking noise almost sounding like a rod knocking. I started my truck up today and waited for it to start making the noise again because it only does it every so often and noticed that my number 2 idler pulley randomly starts vibrating and knocking on something and I wasnt sure if this was just a tightening issue or if it needed to be replaced.

I have a 2005 V6 6 speed 4x4 if that helps. I did recently change my alternator due to some deep water mudding activity and maybe that also ruined this pulley. I'm about to go check the torque which I know should be 29 ft-pds. In the mean time, any thoughts?

 

Awesome thats what I was thinking because it was torque right. Looks like I get to tackle that when I get back from colorado springs. Thanks I really appreciate the input.

 

Hmmm...Metal on metal rattling sound??