Im thinking about buying Mag High flows and was wondering if the O2 sensor was in the cats or in front of it? What model would be the right fit also? I drive a 2001 screw 4.6l v8 and this would be very helpful. And I will pass emissions with just two mags versus the 4 stock (which i think was a stupid idea to do) PLEASE HELP!!!

 

There are 4 sensors. 2 are in front by the exhaust manifold, 2 are behind the cats. The 2 front sensors are the most important. Alot of people have replaced with high flows, most have no problems, some do. Most also do alot of other stuff while replacing the cats, so who knows what combination of stuff could cause a problem. I just ordered my high flows, magnaflow 59959 spun cats, 3". Seems like any magnaflow is a high flow cat, just make sure you get the right diameter pipe, 2.5" is probably what you have stock, and the right size for your engine. Go to planetmagnaflow.com to browse, they have the best pricing and ease of sight navigation.

EDIT: if you just replace your cats, all 4 of your O2 sensors will remain more or less in the same place.

 

The rear O2s are not on the cat, but need to be that equal distance away from the new cats. Go ahead and get the cats.

 

To add to the original question instead of starting a new thread... if I simply have a shop cut out the 2 stock cats on my 05 F150 and weld in two Magnaflow HF cats, will they need to move or otherwise do anything to the 02 sensors?

I've been thinking about this after having my Flowmaster SI/DO installed, but don't want to do it if it will throw codes or otherwise complicate my life. The shop that will do it also said that it will make a minimal difference, if any, going to high flows.

Thanks for the help, any input appreciated!

Will