exhaust where to go

[pontiacman469]

So this cpu stuff is new to me.My 99 5.7 has factory manifolds y pipe and 4 o2 sensors.Now being a 99 the o2 sensors and cat are in need of replacement.Trying to keep the cpu system intact i would like to redo the exhaust,was thinking long tube headers going into 2 1/2 dynomax but that setup only has buns for 2 sensors in the headers,where oem has 4 2 upsteam and 2 downstream can i do this with only 2 o2 or do i need 2 run 4 o2 the readings are not gonna be different if i put 2 more downstream

 

[bigfootchiro]

You will need 4 O2 sensors. If you only run 2, you will need a special tune from someone like @BlackBearPerf , or others, in order to tune those downstream sensors out. At that point in time, you might as well do a cat delete, and have fun! I'd talk to exhaust shops near you and see who can build a system for you without cats.

 

[bigdog9191999]

it can be as simple as adding a bung post cats if your keeping them, if not then have them tuned out and be done.

 

[Eman85]

I'm in a state where there is no inspection and no one cares. My 98 has no cats but still has the rear O2 sensors but never sets a code or turn the light on. If you know a PCM programmer they can tune to eliminate the rear O2 sensors. If you live in a place that has emissions inspection you have to follow the rules.