I've done the muffler, intake, synthetic everything, but the only real performance enhancer I've done has been changing my gear ratio. Throw the other mods out the window and save up for new gears. Saving up for gears may not be instant gratification but a new muffler or intake is not going to give you any gratification when your buddy continues to waste you on the hills. V-10's love gears that get them into their sweet spot.

New 4x4 gears ~ $1500 - $1800