Well, let me tell you what I have. 1994 Cheverolt 2500, 305 v8 with the 4L60 Tranny and 14 bolt rearend. I have recently added a set of pace setters shorty headers, but I also wanted my friend to add a y-pipe that had no cat. He told me since my o2 sensor is directly in front of the cat, it would trigger the check engine light to come on. I was wondering if this is true or not...

 

Not true. The O2 sensors that sit downstream(after the cat) are the ones that tell the computer whether the cats are working properly or not. So you can leave the cats off and not worry bout it.

 

I know that's true, but I was wondering because of the cat making some back pressure before the o2 which is forward of the cat, would that hold true as well.

 

All the O2 sensor in front of the cat does is measure how much oxygen is in the exhaust. The air/fuel ratio is mainly adjusted but this sensor. It tells the computer how much fuel to use. Since you dont have any sensors after the cats, you aint gotta worry bout nothing. That is how mine is set up, no cats. Been like that for 3 years now and no problems. Mine is a 2001 5.3l

 

So what you're telling me is, no idiot light on??? RIGHT@!

 

Right