Installed the K&N 57 on my '03 Chevy Silverado 2500 HD Duramax diesel w/Allison transmission. Improvements were immediate and noticeable. Acceleration from idle and at speed was impressive and shift points were quicker and firmer. Installation was pretty straightforward, and the parts were generally of good quality. An easy DIY project that should last the remaining lifetime of the the vehicle. Overall a great high value upgrade.