Our BPP Cylinder 4 Coolant Mod kit was designed to increase coolant flow to cylinder #4 head area. The additional coolant flow helps reduce cylinder #4 coolant temps and keeps the temps more uniform with the rest of the cylinders. This helps reduce knock and detonation in cylinder #4, which is known to cause the dreaded EJ ringland failure. Keep your EJ happy by installing our kit. Quality was our #1 priority which is why our kit includes CNC'd billet aluminum head and T fittings along with a multi-layer silicone hose and stainless steel clamps.