The PPE 116120000 Replacement Up-Pipes for your 2001-2004 GM 6.6L Duramax increase flow, and reliability. Even a stock Duramax can produce high temperatures and pressures that cause OEM up pipes eventually fail from constant temperature and pressure fluctuation. PPE has taken the OEM replacement to a new level. PPE OEM Up-Pipes allow 53% greater flow over stock, and are a direct bolt-on to your factory manifolds. But unlike factory parts, PPE OEM Up-Pipes are manufactured from 11 gauge 304 stainless steel and include PPE's superior 304 stainless steel, internally-sleeved bellows that can take the abuse of high temperatures and pressures. Uses stock exhaust manifolds and hardware. FEATURES: Bolt-On Replacement (Non-EGR) Faster Spool-Up & Increased Performance Significant Reduction In Exhaust Back Pressure Free-Flowing Stainless Steel Inner Liner Bellows Stainless steel 11-gauge .120-inch wall, 2-inch OD Up-Pipes Note: These race up-pipes do not retain the use of the EGR. They are for off-road use only and will only work on non-EGR applications. CA Residents: Not legal for sale or use in California on pollution controlled motor vehicles.