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1998.5-2004 5.9L Cummins On 1998.5-2004 5.9L Cummins you will need to physically modify your wastegate to gain more turbo boost. Doing this without the Boost Fooler will result in check engine lights and codes set into the computer. Stock 98-04 trucks should generate 18-23psi of boost pressure stock (depending on year model). With the Boost Fooler you will be able to run 35+ psi of boost depending on your fueling enhancements. 2004.5-2007 5.9L Cummins "600" and "610" Series Engines The 2004.5-2007 5.9L Cummins uses an electronic wastegate which is operated off of the MAP sensor. In this instance no modifications to your turbo will be necessary. Stock 04.5-07 trucks typically spike up to 32psi of boost pressure. With the Boost Fooler you will see up to 40psi of boost on a stock truck and up to 48psi of boost on heavily fueled trucks. | 
