The Power Pup Downloader is a programmer/tuner that downloads horsepower and performance enhancing programs into '01-'07 GM Duramax with either a 6.6L (LB7, LLY, LBZ, or LMM) diesel engine in one SKU (stock keeping unit). The Power Pup will also work on the '06-'07 4500 and 5500 series vehicles as well. The downloader offers up to three different Engine Tunes above stock to accommodate various driving conditions. Stock: Choosing the Stock engine tune will result in no change to engine horsepower output. All other downloader features can still be accessed if the Stock engine tune is chosen. Tow: This engine tune is recommended for use while towing, it is a mild tune that increases performance by 40 to 50 horsepower. This is the only tune that we recommend you tow with other than stock. Performance: This engine tune will yield up to 75 extra horsepower. Pyrometer and boost gauges are highly recommended while using this tune. Extreme: This engine tune will yield up to 120 extra horsepower. Pyrometer and boost gauges are highly recommended while using this tune.