The CP4 introduced in the Duramax platform with the LML has proven to be much less reliable and less capable than the CP3 found in the 2001-2010 Duramax's. When a CP4 fails, and many do, It is extremely costly to fix and requires replacement of the entire fuel system which can cost 10k dollars. Fleece Performance has created the cure for this by engineering a conversion kit to go back to a CP3.