Exhaust Headers for Lexus IS300 (2001-2005) 3.0LHigh Flow Exhaust Headers for 2001 2005 Lexus IS300 Directly replaces the restrictive factory exhaust manifold to improve exhaust gas scavenging and reduce cylinder head temperatures. The Stock IS300 Exhaust Manifold Bottleneck The factory cast iron exhaust manifold on the JCE10 Lexus IS300 is engineered for mass production and extreme noise suppression, compromising volumetric efficiency. Over time, these heavy cast manifolds are prone to heat