It depends on what you’re after! A flash tuner is geared towards top end power, whereas the Stealth Module works at your low to mid range RPMs. This is where 99% of your driving occurs. The Module is a non-invasive device that requires no flashing of your ECM or other modification. It is a safe way to get better performance out of your Cummins, Powerstroke, Duramax, Nissan Titan or Land Rover without sacrificing your warranty.