After a downpipe or cat delete, the rear O2 sensor often triggers a check engine light. RVNG O2 Spacers fix that by moving the sensor slightly out of the direct exhaust stream so its readings stay in range and the CEL stays off. Every spacer is inspected for defects before shipping.They're effective 100% of the time on twin-turbo vehicles and about 85% of the time on single-turbo cars — depending on the tune and setup, a single-turbo car may still throw a code.Effectiveness Twin-turbo vehicles — effective in essentially all cases Single-turbo vehicles — effective in roughly 85% of cases Emissions disclaimer: This product is not legal for sale or use on pollution-controlled vehicles operated on public roads and is intended for off-road, race, or closed-course competition use only. You are responsible for compliance with all applicable emissions laws; use on public roads may violate the Federal Clean Air Act (42 U.S.C. § 7522) and similar state laws. Please check your local laws before purchase and installation.Ships from our Vancouver shop — KORE SPEED is proudly Canadian-owned, with no surprise cross-border duties for Canadian buyers. Questions on fitment? Email [email protected].