I am wanting to put some high flow cats on my 04' 5.4L....I have a cat back exhaust but wanted to replace stock cats for some magnaflow high flow cats. If anyone has put these on, what are the part numbers for the cats you used, and did they make a difference? Thanks

 

I am also interested in at least researching this for when/if my cats do need to be replaced...

 

Many use the 94306 Magnaflow, however I'd also consider the 99236HM series cats. The difference will be louder volume and different tone depending on what the rest of your system is.

Only reason to is if there is an issue or you want more sound.

 

Yeah, I just like to have an idea of stuff to do for if/when something goes wrong.

 

I have Magnaflow 94106 and love them. They are a strait through cat and made my truck have much more volume. Thats the only way id go if I did it again.