2003 - 2007 5.9L Cummins

The new fueling strategy included solenoid-activated injectors, an updated cylinder head, and a stronger 5.9L engine block. The injectors were 8-hole (2003-2004) and 5-hole (2004.5-2007) designs which, once again, helped with emissions. The new cylinder head featured a rocker box that accommodated the injectors and crossover tubes as well as heavier-duty intake and exhaust valves.

From 2003 to 2007, Cummins offered two different turbochargers for its 5.9L engine. A Holset HE341CW was used in 2003 featuring a mechanically controlled internal wastegate that holds higher-than-stock boost pressures.
However, to better comply with emissions regulations, the 2004.5 to 2007 engines came with Holset’s HE351CW. This turbocharger is similar to the HE341CW but the wastegate is electronically controlled. This new turbocharger allows for a noticeable boost in performance and lowered emissions output.