Rear 02 sensor mod (spacer), easy bolt-on kit installs inline with the rear 02 sensor on the 02 bung to prevent the CEL due to racepipes. Off road use only. This mod is only 90% effective as variation in rear 02 sensitivity varies from car to car. No Guarantees. Tested and works well on all VW / Audi vehicles from 1996 through 2007.

Good compliment to these racepipes:

ATP-VVW-138 Audi A4/Passat (B5)
ATP-VVW-139 3" Cat delete Racing Downpipe $165.00
ATP-VVW-170 3.0" Downpipe Assembly for FWD 2.0T FSI Turbo
ATP-VVW-190 3" Stainless Cat Delete Upper Downpipe, Audi A4 B7 2.0T FSI