im thinking about getting my dad a smarty for fathers day. i was wanting to see some others opinions on it. he has an 03 dodge 5.9 cummins quad cab dually with a K&N air intake system and an edge chip set at 75 hp. the rest is completely stock. i want to make him happy and give him something that 1. will make his fuel economy go up and 2. will provide him with the ability to chuff when he wants. any opinions?