Exhaust Manifold Headers Shorty for Ford Mustang GT & Cobra (1996–2004) 4.6LHigh Flow T304 Stainless Shorty Headers for Ford Mustang 4. 6L Replaces the restrictive factory cast iron exhaust manifolds with mandrel bent shorty headers to improve exhaust scavenging and lower engine bay temperatures. The Stock Mustang Restrictive Airflow The factory Ford Mustang 4. 6L cast iron exhaust manifolds are notoriously restrictive, plagued by rough internal casting flashes and sharp log style bends. These manufacturing compromises create