Performance Valve Springs and Retainer Kit XDPFortify the valvetrain in your 1989 1998 Dodge 5. 9L Cummins when you install the XDP Performance Valve Springs and Retainer Kit XD389. Valve springs are a vital upgrade that are often ignored in many performance builds. The stock valve springs in your Cummins engine are not designed to handle the increased engine RPM or higher boost levels that are common in modified applications. Even typical upgrades like an exhaust brake, aftermarket turbocharger,