2004 F-150 cat converter question

[ProZach]

Quick question about the four cats on my year's truck.
I know that the first two are the typical DO NOT REMOVE under penalty of law kind of cats. But are the back two some kind of other cat? Someone told me that there was a possibility that they were "resonator cats" and that if they were I would be able to take them off legally.
does anyone know if this is true?
can someone tell me if there's even a difference between the front cats and the rear cats on my truck?
basically I just want my exhaust to sound better like this guy (same year and body style) http://www.youtube.com/watch?v=oNNu68iQ7xY&feature=related

[YT]oNNu68iQ7xY[/YT]

So in a nutshell I just want to know if they are different, if its illegal to remove the rear two, if I have to worry about any sensors if I do this, and if it will help performance at all (rumor on one of the sites I was browsing said a dyno chart had 20+ hp from removing them but I'm not prone to believe this, just curious)
any and all help is always appreciated.

ps I know it will take more than just cats to get my truck to sound as good as the one in the video, just thought it would be easier to do the cat removal first (or at the same time).

 

[Ricky Bobby FX4]

technically its illegal to remove any of your cats. the front cats are pre cats and the back 2 are regular cats. you can remove them I am some time soon.

 

[mrolgren]

I'm not very well researched as I have an '06 F-150 so I only have 2 cats but from what I understand the legality of it is a bit of a grey area. Most people over on F150online cut them out and add in a piece of pipe. Some run into O2 sensor issues but some don't.

Most people say that it won't gain you much of anything (HP or MPG) but it will make your exhaust sound better.

Here is a writeup somebody made on their Rear Cat Delete.

Hope this helps!

http://www.f150online.com/forums/exhaust-intake-systems/343787-finally-deleted-rear-cats.html

I've posted links from other forums before but I'm not sure how "legal" it is... Can one of the Clowns weigh in on this for me please?

 

[Bigredmariner]

Yes it is "Technically" illegal to do anything to the emissions of a vehicle.

That is Darren's truck and he'll probably weight in here, but it is probably the best sounding F-150 out there.

I have no problems with links to other sites when they are helping out members.

 

[Carolinaboy]

I agree He and I have the same setup, but he did Highflows IIRC

 

[buckshot85]

yea just cut off the 2nd two like most people. and leave the first 2 or either put highflows on them. i have the same set up darren used to have and it gets loud as **** and sounds good

 

[Shanks12]

You can't go wrong with Darren's setup... Hell It inspired my setup!


2.5" True Duals
- High Flow Cats
- X Pipe
- DynoMax Bullets
- 4x 18" Tips 45'd out the back


I think Darren has the exact same setup but without the High Flows..


Edit... This is his old exhaust, so this is with the MagnaPacks

2004 Ford F-150 Super Cab XLT 5.4L 4w75e trans 3.73s 4wd.

stock manifolds
deleted rear cats
2.5 true duals X piped
Magnaflow 11 body mufflers
Magnaflow 4x18 rolled tips 45'd

 

[Shanks12]

This is his new exhaust...

2004 Ford F150 Supercab 5.4L 3.73.
stock manifolds
deleted rear cats
2.5" true duals X piped
Dynomax Bullets
Magnaflow 4"x18" tips.

[YT]Jo4eXYrCwRQ[/YT]



But back to your question, I think Martin said it best... You won't be gaining 20HP but it will make the exhaust sound better. I had just 2 cats on my setup before I switched but the previous owner put a cheapo exhaust on so Im not sure if mine had 4 to start with.

I guess you would just need to crawl under the truck and see if you have o2's in the back and if so you can have a tuner (if you have a tuner on your truck) do an o2 delete on the back I am pretty sure.

 

[ProZach]

This is his new exhaust...

2004 Ford F150 Supercab 5.4L 3.73.
stock manifolds
deleted rear cats
2.5" true duals X piped
Dynomax Bullets
Magnaflow 4"x18" tips.

[YT]Jo4eXYrCwRQ[/YT]



But back to your question, I think Martin said it best... You won't be gaining 20HP but it will make the exhaust sound better. I had just 2 cats on my setup before I switched but the previous owner put a cheapo exhaust on so Im not sure if mine had 4 to start with.

I guess you would just need to crawl under the truck and see if you have o2's in the back and if so you can have a tuner (if you have a tuner on your truck) do an o2 delete on the back I am pretty sure.

yeah I saw his dynomax video but I personally like the magnaflow sound that he had previously.