I have a 2004 S4 6MT

Okay, so I've searched google, VWVortex, and Audi Forums for info on a DIY for piggies for the B6 model s4. I know how to remove the downpipes (found that thread)

And I figured out a fast way to get the precat removed once I have the dp removed.

So I can remove the DPs and I can gut the precats. But from there, I'm just no connecting the dot with the CEL and the O2 sensors. I understand that there are 4 O2 sensors? 2 after the precats and 2 after the main cats? Do I simply buy a set of spark plug defoulers and put them into the openings for the precat O2 sensors? Do I have to move them closer to the main cats AND space them?? Should I get the VAST spacers instead?

I've read that you sometimes will get a CEL anyway, even if you space the O2 sensors.

If I go to the trouble of pulling my DPs and gutting them, what do I need to do to the sensors to avoid a CEL?

 

i'm not sure exactly how you do it but i know JHmotorsports does it and they can also tune the ECU to not throw any codes with no cats at all, pre or regular. They did my piggies and ecu and no codes. They are very helpful with techincal questions. it will definitely be worth e-mailing their V8technician, they have helped me several times, customer or not.

 

In principle: de-foulers and tuning the rear o2 out are the common options.
On our other car (Cougar 2.5 Duratec), we followed a DIY describing to solder in some resister (IIRC) to trick the downstream o2 and deliver values it expects.
Don't know if our Audi's can be done this way.