For customers who want to tune or adjust the power steering system to maximize assist and road or track handling, we suggest our New Flow Control Valves for the FR1590 KRC Pump. The valves are similar to jets in a carburetor. The I.D. B-E will improve assist, while the I.D. 4-7 will improve road handling. The lower the number, the greater the feel, but less assist. The higher the letter, the more assist, but less feel. Keep in mind that adjusting your steering assist or stability is about finding the correct balance for your driving comfort.