[pokeybritches]

I'd guess 360 hp, +/- 5 hp

You need a before/after dyno ramp run to determine the % gain.

MAF-based systems do a decent job taking into account certain types of mods, because they measure the airflow increase and can add more fuel. You might pick up a few hp with a tune. If you modify the intake, or change sensor locations (like O2 sensors on aftermarket headers), you're more likely to need a tune. If you had an alpha-n tune, you would definitely want a retune with any hardware change.