How many miles on the car? is this a limited or srt 6? I have my cats that came off my srt6 at 30000 miles but will sell in pairs,, both rear's or both fronts. $300 for either fronts or rear or $500 for all 4 ,,+ shipping. now for my thinking,,change your oil use moble 1 0-40 maybe the ticking, they all tick but not too loud.
do you have an engine light on if yes what code?
I really believe your 02's are ok and throttle body is ok too if it is a srt then you most likely need a supercharger pump
also do the throttle reset. (search throttle reset.) dis connect batt. for 2 to 4 min this will reset most everything. tell us also in the 6 months did u have any problems? jim