Injen RD3020P: Air Intake Volkswagen Jetta IV VR6 2.8L 99-02, RD Series Polished Cold Air Intake System (RD3020P) by Injen. The RD Series is made for the enthusiast who wants improved mid-range power. This cold air system positions a high-flow air filter behind the bumper, where it can take in cooler, denser air. The cool air then flows to the engine through a fee-flowing aluminum alloy intake tube. Cooler air contains more oxygen for more complete combustion and more horsepower.