take a look at Todds post
http://forums.audiworld.com/s4/msgs/465188.phtml

AWE dp's DO require a recoded chip...

"The improved flow allowed us to increase upper rpm boost, while requiring us to adjust fueling a bit higher. We believe that a properly tuned downpipe system *requires* the use of a specific downpipe chip if the downpipes are doing their job of improving exhaust scavenging. Our design requires a change to the O2 sensor coding, too, as we opted to place the O2 sensors close to the OEM position to maintain proper tension on the wiring.
"