As 'crewchief' said: even on a stock motor you will find gains with a Tune. Although modifications in conjunction with a tune will unlock even more gains.
You can expect an increase in Horsepower, an improvement in torque, better fuel economy and even a more responsive throttle.
if nothing else, a dyno will show you if youre down a cylinder or running lean due to fuel pump issues and whatnot. its a good test to check if everything is working as it should IMO and money well spent.
If I was going to It over again I`d get one of these HP tuners/vcm suites or EFI lives flash scan. If you are computer literate that is, also there is plenty of help on the manufactures website including forums too.