To be honest, I'd save up and get the tuner or get a dyno tune. Not only can you alter stock settings like the governor and rev limiter, but depending on the type of tune you can gain some noticeable hp and tq. The biggest difference will be in your transmission. Autos are significantly changed for the better after a tune. It will feel like a completely different car.
12 Black GT500 SVT PP l 2.6 Pulley/Idler l Airaid l o/r X l 305 NT555R's l Recaros l
04 Azure Blue Mach 1 / 03 Sonic Blue 3.8 / 14 Sterling Grey F150 FX4 402A 5.0 / 11 GT500 R.I.P.