Re: which new mod?
For the money spent on fuel rails or a new throttle body/plenum, you could get a set of gears thrown in and "feel" more gains. The taller gears will provide better power throughout the powerband, making launches and low end acceleration much better.
Keep in mind that you'll need a tuner to adjust the speedometer for the gear changes. You can also add your other bolt on mods like exhaust, CAI, and udp's to the tune to make them more effective.
Gears are ~$150, install is $300-500, and a handheld tuner with CUSTOM tunes from VMP or American Muscle is ~$400.
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.