i have found the hi flow cats by magnaflow that have o2 sensor inputs for 2004 and up.
http://www.planetmagnaflow.com/shop/...eries-105.html
i would use the midbed o2 sensor since thats where it is located on the stock one. EXCITMENT!!

 

These trucks need part # 94306. The OEM cats do not have the O2 sensor mounted in the rear cats so they should not go in the new cats. Put them in 1 - 2"s further back as they are stock.

 

i have an 01 with the O2 sensor in the rear cat. Should i not get a high flow with a hole for the O2 sensor?

 

so your saying that you shoudl not put the 02 sensor in these cats? i want to take all 4 of mine out and put high flows but i am confused as to what to do with the 02 sensors.

 

If the OEM cats have the sensors in the cats, you need the Hi-Flow cats with the O2s mounted in them.


Not if the OEM cats do not have the O2s in them already. My 2004 has the rear sensors mounted before the rear cats, so therefore I do not need them, and you wont most likely since your setup should be the same as mine. Chief_321 just stated his 2001 has them mounted in the rear cats, therefore he would need Hi-Flows with the O2 mount.

 

ya mine are like yours. the sensor is mounted in between the front and rear cat. so if i got high flow cats where do i mount the 02 sensor? because i would be taking out where they mount now to install the new cats.

 

I believe they go in the same spot, 1/2" before the cat. If not, then 1/2" after the cat. I'm a bit confused when it comes to the sensor mounting situation, but I know that we need part # 94306.

 

the 2004 have 2 cats, the reduction cat and the oxidizing cat, in the 2005 and up both are contained in one case with an air gap in between which is why the sensor is located in the middle of the cat(after the reduction cat and before the oxidizing cat) same thing different desighn. so its pretty much the same just looks different, hope that clears things up.

 

There are upstream and downstream 02s on our 2004 trucks. They are before and after the first cat. The second cat is just there. I cut the back ones off and it did nothing as far as 02s and codes. So my guess would be to sandwich the high-flows between the 02 sensors (since my 2 remaining cats are that way).

 

^^ i noticed you live in california. you will fail emissions tests with rear cats removed.

 

Normally, that would be the case.

But most of the time they just do the OBD2 test, and no codes will pop up. They rarely check underneath.

It only takes about 15 minutes to weld them back in. Very easy to do just for emissions testing every 2 years.

 

i don't think there would be enough room to put a biiger high flow cat between the 2 sensors.

 

Well I think you could space out the sensors to fit a larger length cat in.

mSall150 so you deleted the rear cats? as in the longer ones, and left the pre-cats? Still run good and the CEL is not elluminated? I'm probably going to be looking to have high flow cats installed but if the rear cats can be deleted and no O2 sensor or lag in power, i'll have to try that out before I spend $174.00

 

Yeah i took out the ones behind the downstream 02s, so there is no CEL. left the precats since they are between all the 02s, didn't want to mess with those. No CEL yet.i'll give you an update after a couple weeks to see if anything happens. i'll try to get a soundclip too if i find my camera.

 

Awesome thanks man much appreciated. Anxious to hear that Roush Off-Road muffler too.