Hey guys, I am fairly new here and have been considering doing a new exhaust setup on my 1999 4.6L F-150. I had in mind of doing longtubes, into high flow cats and than true duals into an x-pipe, siso mufflers and out... However, talking to my muffler shop here in Boulder CO, I was told that I wouldn't pass emissions if I changed to high flow cats. The 1999 F-150s had 4 cats on them, essentially a pre-cat and a cat for each header. I am wondering why I can't replace those cats (both the pre-cat and cat per header) with a single EPA compliant high flow cat such as this on: ? I would then run the pipes downstream of the cats into the x-pipe and so on. The shop here just recommended to take out the Y-pipe and run the pipes into a DIDO muffler to act as an x-pipe and then run the pipes out. What option should I go with?

My plan for this system is to get a performance increase while also making the truck a bit louder, am I going down the right track?

Thanks in advance for your guy's help!

 

Headers and high flows really aren't worth the money, you really won't get better performance without more mods.

Cutting the Y-pipe and getting a DI/DO with internal X-pipe is the most economical way to get a slight improvement and better sound. Your muffler shop is on the right track. Then do a Gotts mod to the intake air box. A programmer with custom tunes will give you a lot more performance increase than any exhaust or intake mods.

 

Hey glc,

Thanks for your fast response, how do you recommend I get the tune/programmer after all the upgrades are done?
Thanks

 

https://www.f150online.com/forums/ch...unes-read.html