The 2002-2005 Audi A4 quattro combines timeless Audi design, turbocharged performance, and legendary all-wheel-drive capability. Enhance your A4 quattro with APR performance upgrades, including ECU tuning, intake systems, exhaust upgrades, turbocharger enhancements, and supporting hardware engineered to increase power, improve responsiveness, and maximize driving enjoyment.

APR’s diverter valves embody the highest standard of boost control engineering — precision-machined billet construction paired with a Nomex-reinforced diaphragm design, delivering faster response, zero piston-stiction and reliable performance even under extreme boost demands.