Get a handheld tuner. I have a SCT X3 and a 93 octane tune from Justin at VMPtuning. With the 93 octane tune, he adjusts the timing to increase power. I'd say i gained about 15-20 hp with the tune.
__________________ 2002 Auto V6 Mineral Grey Mustang:
Go mods: U/D Pulley, BBK CAI and 65 mm TB, Pypes Violators dual exhaust with stock cats and an h-pipe, upper intake spacer, j-mod, SCT X3 tuner, and 3.73 gears and t-lock.
Show mods: Sequential tail light kit, GT fog lights, 8" shorty antenna, hood shocks, HID headlights, 17x9 inch Mach 1 rims wrapped in Vredestein Ultracs, and a chin spoiler. | 
2004 Mustang 3.9 V6 Timing 
