+1This exhaust with a power commander and a good map will surprise you.
personally I try and avoid the "ricky racer" mods... (defined as mods that may net 1 or 2 additional hp at the expense of low or mid power but might pay off on a "race" only motor)
A pipe, PC3, custom map and a gear change seems to me the most "productive" mods that seem to help everywhere...