So I am curious. You guys that have cut the back cats off, how do you run the o2 sensors without a cel? Or am I mistaken on which cats are actually cut off? I plan to run true duals with dynomax bullets VERY soon, and if I think they're too quiet, I'm gonna go other routes to make it louder. Anybody got a clip of a 4.6 with these mufflers straight out the back? I have one on my dsm and love the sound of it, especially under boost Sounds insane.

 

2004 & 2005 4 cat systems can have the rear cats removed simply. The rear O2s are infront of the rear cats, so removal of them will not have any chance of an engine light.

Check out my thread about my experience and view the photos.
https://www.f150online.com/forums/ex...rear-cats.html

 

I guess I should have said that mine is an 2003 4.6 truck. Seems like I read that my model has the cats backwards from yours? That I need to take the front ones off and leave the back?

 

DarrenWS6, did you cut off your cats, and if so can you see a big performance gain?

 

I deleted my rear cats, slight noticeable difference, and a helluva lot louder and deeper. No CEL after 1 month.

 

I gutted all 4 of my cats, welded a pipe in them so they still pass 'visual' inspection. I had to buy MIL eliminators. They keep the CEL light off. BTW, mine is a 2000 5.4.

 

I removed the rear cats since they weren't O2 monitored and resonated alot of sound. I have true duals so I lost quite a bit of power, but I did feel a gain afterwards. Before from a full stop, WOT wouldn't screech the tires, but i can screech them now.

 

I'm somewhat confused. Is it the converters that have the o2 screwed into them that you guys cut off with no issues, or is it the other set?

 

And do you just have a piece of pipe welded in each spot?

 

1997 - 2003 = rear O2s are after rear cats.

2004 - early model 2005s = pre-cats monitored only, rear are not monitored

2005.5 - present trucks have 2 cats with rear O2s mounted in the centers. The un-monitored end of those cats resonates sound so theres no reason to monitor it. Putting hi-flow converters in then mounting O2s after them will keep the light off, put putting pipe in will set the CEL since there isn't any catalyst monitoring the gases confirming they have been burnt and filtered.

 

How would stock exhaust sound with rear cat delete?

 

would still sound stock, just more whistley if that makes sense.