I have '99 A6 avant 2.8Q tip 95k miles, Cats are gone, rattling alot, if I just gut them will it trip cel? Is there a dummy o2 sensor that will allow this to work? I have emissions testing in my area, but they only plug in computer and do visual under car, no tail pipe test. Will this work or should I just replace cats?

 

It will more than likely trip your CEL. Even if it doesn't it will kill your gas milage.

The best thing you can do it go ahead and gut them but then use a small piece of pipe thats 2.5" long and tap it out to screw it into where your O2 (after cat) then screw your O2 into that. It will trap air and trick your CEL.

This is what we do on celica's to trick the ECU and it works!

 

Hey that's a pretty good tip, I've never heard of that before, thanks