Description: All models. 7.4l. With 7.4L, gas. 4.6L. Express, savana. 7.4l. Seville. 3.5l. Aurora. 4.3L, cpi. Helps provide a leak-free seal Allows exhaust pollutants to enter the engine for re-burn Helps the engine emission system operate properly This GM Genuine Part is designed, engineered, and tested to rigorous standards and is backed by General Motors