A programmer is used in conjunction with a delete kit. Warranty issues for sure when something goes south. A programmer will simply force the timing to advance, increase fuel flow from the injectors while creating higher temps even though u may not see those due to the newer cooling system. Some tuners will destroy the injectors over time due to the higher fuel flow/pressure being exerted on them. With the newer diesels already powerhouses I personally would not mess with it. Today's computer systems are a tell all to the dealer during warranty claims, and the tune even if deleted will show in the history. Just my opinion, but with the prices of Diesel engine and components I would leave it alone.