The 2.3-litre EcoBoost engine in the Focus ST Mk4 is a strong foundation, but pushing for extreme horsepower levels requires a reinforced bottom end to handle increased cylinder pressure. Safely push the boundaries of your Mk4 ST by installing heavy-duty Forged Conrods and fully Forged Pistons. Secure your engine block with high-tensile Engine Bolts, race-spec Engine Bearings, and high-pressure Engine Gaskets. Replace restrictive or fragile factory lines with durable Engine Hoses, and complete your custom engine assembly with our wide range of Misc Engine Parts engineered for high-output builds.