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ORIGINAL: backinblack700

 i have 3'' straights from the headers out the back on my '94 5.8L F-150, no cats or mufflers with 6'' tips, its crazy loud...

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ORIGINAL: HondaGuy

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ORIGINAL: nonnieselman

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ORIGINAL: HondaGuy

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ORIGINAL: BTTW

when you gut the cats (i do this so it still looks legal lol), as i have on old 5.7TBIs and 4.3vortecs, as said above it messes with o2 sensors, which cause it to think its running lean and it dumps more fuel which not only smells but mpg goes down. you can get it tuned out/off (the o2 sensors) as said above. Also, the 5.3 i would run a 2" or 2.5" pipe from the cat back(after gutted).  right now i have a NNBS gmc 6.0 with no cat and 44 flowmaster and its LOUD, not poppy either like most people say.

i say go for it :D thats just me though :P

No it does not, the rear O2 sensor has nothing to do with the air/fuel ratio they are a Catalyst (catalytic converter) monitor only. The front O2 sensor is what controls the air/fuel ratio and that is not affected by something you do behind it. I don't have a rear O2 sensor on my truck at all and it runs no different and gets no worse MPG with it gone.

Gah.. im glad your tryin to teach them something.. Some people are just to dumb to listen..

Only thing thats goin to happen to the PCM if you gut/delete the cats is, your goin to throw codes. Thats it.

Here are the possible codes:

P0137       O2S Circuit Low Voltage Bank 1 Sensor 2
P0138       O2S Circuit High Voltage Bank 1 Sensor 2
P0140       O2S Circuit Insufficient Activity Bank 1 Sensor 2
P0141       O2S Heater Performance Bank 1 Sensor 2
P0157      O2S Circuit Low Voltage Bank 2 Sensor 2
P0158      O2S Circuit High Voltage Bank 2 Sensor 2
P0160      O2S Circuit Insufficient Activity Bank 2 Sensor 2
P0161      O2S Heater Performance Bank 2 Sensor 2

I didnt notice any loss of gas mileage when i gutted mine, but i had the full exhaust all the way to the stock tail pipe with just a small magnaflow muffler.
Didnt notice a gain or loss of power either. It made it alot louder tho. Now with the turbo i put another muffler behind it to quiet it down almost to stock levels.


If i were to do it again on a Stock NA truck. I would just gut the cats, and put a decent muffler where the stocker is.
Stock exhaust size is 2 7/8", Its actually Metric but thats what it measures. That will support plenty of flow for even a slightly modded engine.

Thanks for the help, I am trying some people just don't get it, even though they think they do. Have you run your truck at the track? How much faster is it with that STS setup, and how much boost does it make? I'm getting ready to start a custom turbo setup on my 02 Dakota 4.7L rcsb, going to be in the neighborhood of 400-450hp at 12psi (properly tuned of course).