If you don't have a check engine light, it already has a Tune.
Which adds 25 to 40 rwhp depending on Tuner and mods.
You not going to see much more at this point unless you add a Supercharger, like Whipple or Roush.
I'm guessing you bought it used.
I hate when the previous owner/seller doesn't include the handheld Tuner device!!!!
You'll need a good OBDII scanner to get info off the PCM and call the few Tuners I have listed.
Basically, there are a few Tuners of which three are still making Tunes, JDM, 5Star and Livernois.
SVC, no longer offers Tunes, which is a shame, they were the best!!!!