s4 4.2 v8 decat
 

Thinking of ditching the cats on my v8, i know the legal mumbojumbo but need some info, is removing the cats and relevant sensors going mess up the fueling and ecu? images of my car going Ahhhhhhhhhhhhhhh! with lots of blinky lights on the dash come 2 mind.

why dont you get high flow cats from like magnaflow or somthing??
i've heard it'll mess with the ecu! but i dont have any exp with this so....

High flow cats cost a fortune when u can replace them with pipe 4 next 2 nothing, as long as it works, im hoping that retaining the sensors may be the way 2 go, has anyone got any more thoughts on this before i start cutting my exhaust up on a whim

oh yeah true!
well if you do it, let us know how it goes? (if it messes ur sh|t up..?)

I would be very very careful. Dont forget those sensors are o2 sensors which will change the tune for rich or poor. The reason those cats are there are to keep emmissions down by tuning the car for the enviroment. If you take those the stock ecu tune wont like it and run the car lean thus throwing a cel. If you want your going to have either a) Get it tuned, B) Trick the O2, or C) get high flow cats.

The fuel mixture is determined by the primary 02s, before the cats. What you're going to screw up is the fact that the secondary (after-cat) sensors are there to monitor the effectiveness of the cats. Soon as you delete them you're going to throw emissions codes which you cannot get rid of unless you reinstall cats again. Until you do that, you'll be driving with a check-engine light and you will NOT pass inspection, either smog or visual.

All of this is found using Search - it's been covered numerous times.

For the record though, decatting the V8 S4 sounds mean as hell. Search YouTube for "S4 no cats" or something like that and you'll find videos of it.