mid pipe for the power and to wake up the stock mufflers(they dont sound shabby...just a catback nets you 1 hp and sounds like ass without a midpipe)
gears if you want a quicker launch, wont gain you hp but will make your 1/4 mi times faster by about .3-.5 tenths of a second
NOS, if you want quick HP gains
with all the new found power you will want to invest in a short throw shifter
DONT invest in a CAI for HP gains. it isnt cost effective
shocks and struts and springs. if you want ONE OF the best go with a set of HD Bilsteins(~$600), i will be picking up some in a few weeks. springs, its up to you how far you want to drop it. H&R super sports look AWESOME on our cars but i went with steeda sports which is half the drop only because im not just after looks
tb/plenum is another nice mod that will give you a quick 10hp for a 20 min install. there are many companies that make these but top of the line right now is accufab for performance
handheld tuner great for code reading and much more like adjusting speedo for bigger wheels and gears etc....if i were to be getting one id go all out and get SCTs LiveWire
more to come as i think of them