Can the Cat Convertor and stock exhaust on a 2004.5 LLY be removed and replaced with a staight pipe and magnaflow muffler without engine codes and other undisireable things happening? Sorry to post so much but I would like to know as much as I can before starting any modifing.


Thanks for the repliesEdited by: AbsoluteGMC

Why bother with a magnaflow muffler, id just straight pipe it completly. As long as there is no oxygen sensors or anything in the cats, you shouldent have any trouble.

Jury is still out on the removing the CAT question in regard to setting codes.


Those who've done it seem to like the change, but about 2/3 of the trucks are setting codes with the CAT removed. Others are not. Doesn't seem to be any way to predict which truck will or won't. Doesn't seem to be isolated to one particular exhaust system or truck configuration.


Just have to try it and see. Worst case you could just re-install the front pipe with the CAT in it as some have done when their trucks kept setting codes. Others have just ignored it...http://www.dieselplace.com/forum/smileys/Ermm.gif


So there's no absolute answer to your question. Try a few searches on it and you should be able to get quite a bit more info about what various members have done and the results they've gotten.Edited by: Zeeb