DIESELR Cast Iron High Flow Exhaust Manifold (2003-2007 Cummins 5.9L)Built to Perform: Engineered to outperform the stock manifold, this heavy duty upgrade boosts exhaust flow by up to 20% over factory. Matched ports and a merged runner design reduce backpressure for noticeable gains in performance and throttle response. Durability You Can Count On: Cast with 0. 25" thick wallsa serious step up from the OEMs 0. 15"to eliminate warping and cracking under extreme heat. The reinforced T3 flange adds strength where it