PDI Big Boss Stage 1 Performance Kit for Cummins X15 and ISXAvailable for: 2010 2022 Cummins ISX15 & X15 Engines **PDI Big Boss Intake manifolds are built to increase performance and balance the air going into the engine. By opening up the manifold in key areas airflow will increase up to 35% leading to lower air intake temperatures resulting in power gains of up to 20hp. These direct replacement manifolds are simple to install and utilize factory hardware. Like all PDI products, the Big Boss intake manifolds