Twin CP3 Pump Kit for the 2004.5-2005 LLY Duramax allows you to mount a second high pressure CP3 pump (available separately) next to your AC Compressor to support larger injectors and higher horsepower. A second CP3 pumps adds volume to your high pressure fuel system to maintain consistent and smooth rail pressure. Our Kits use high quality machined stainless fittings and hardware, heavy duty fabricated steel CP3 mount bracket with powder coat finish, and come standard with our custom machined billet aluminum drive pulley available in raw aluminum or custom powder coated (Extra Charge). Does not work with dual alternator applications