This engine uses two different types of spark plugs, totaling 16 plugs mounted in two rows: the upper row on the intake valve side of the cylinder head uses Bosch Nickel Yttrium plugs, while the lower row on the exhaust valve side uses Bosch Iridium plugs, and these plugs must not be interchanged. Never use a motorized wire wheel brush to clean spark plugs, as metallic deposits can cause misfires, and do not attempt to clean any spark plugs; they should be replaced only. To assist with coil installation, apply silicone-based grease, such as Mopar(R) Dielectric Grease, to the spark plug ends of rubber boots and the tops of the spark plugs. Two different spark plug gaps are used, so check and adjust the gaps with a plug gap gauging tool. Avoid dropping spark plugs into the plug wells to prevent electrode damage, and install them into the cylinder head by hand to avoid cross-threading. Always tighten spark plugs to the specified torque, as certain engines use torque-sensitive spark plugs, and over-tightening can distort the plugs or crack the porcelain insulator. Due to tight clearances between the upper row of plugs and the cylinder head, a deep, thin-wall 5/8" spark plug socket must be used for removal and installation. After tightening the spark plugs to the specified torque, install the ignition coils and then the necessary air filter tubing and air intake components to the top of the engine and to the throttle body.