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I also added a lift pump to make sure that that the increased fuel volume is maintained to keep from draining the fuel rails and taking a chance of damaging the CP4 high pressure fuel pump. I decided to go for a delete tune by disconnecting my DEF pump, removing my DPF, but keeping my cat intact to keep it from droning and smelling like an old piece of mining equipment. I did run an EFI Live based emissions compliant tune, but it did nothing for my frequent regens or dismal mileage. I never had any DEF issues, but my refill warnings started to give me less and less mileage before it would go into limp mode. Yeah, you can tune it with the emissions intact, but you still have the DEF issues, regens, and crappy mileage.
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