I've been hearing some good things about hi flow cats for the F150, but haven't uncovered much on the subject on this board. Has anyone installed hi flow cats on a 5.4L, and which brand did you install. Also, where did you get them, how much, what size, etc. Any information would be helpful. Also, what gains did you notice, and did this change your exhaust note (louder/deeper).

Finally, does my 99 F150 have 4 cats? It looks like I have a pre-cat and regular cat on each side. Does this mean I would leave the pre-cat on and only replace the regular cat?

Thanks,
SlickWilly

 

What little has been posted and that I've read, the OEM flow high enough. They realy arent' that restrictive like the old days. I wouldn't mess with it.

Many people have however replaced the factory "Y". Once you get it off, you'll see what kind of restriction is really there that you can't see from the outside. Definetly something a shop would probably do!

Do a search on "Y" Pipe