PISTON KIT (Low comp) FA20 D8621003 AT004 Capacity Upgrade Kit for FA20 Low Comp High boost tuning in the era of direct injection engines! The low compression type FA20 2. 1L Kit is available for high boost tuning. Upgrading with forced induction is very common for the FA20 engine tuning. HKS has developed a highly durable low compression piston required to move onto the next tuning level. Features POINT 1 Piston Forged material improves durability. The cavity is designed in