recognizing pi heads from non pi

ok, a week ago i traded for a 97 gt that is very fast. my wife got jealous so i traded her car for a 98 model gt that is not nearly as fast. it is quick and both are five speeds. hers is bone stock, and does not have near the power of mine. i know my gears have been modified as now i see that her rpm's are much lower than mine at same speeds. mine is 2500 at 80mph, and hers is about 1800rpm at 80 mph. i have exhaust and cold air intake but i dont think just gears, intake, and exhaust would make the drastic difference in power that im experiencing. i either have atermarket cams or maybe the pi head swap has already been done. can someone tell me if there is an obvious appearance difference in the two heads?

im hoping the swap hasnt been done because that tells me how much power i can get out of this thing by doing it.

if i can find a shop with a dyno im gonna get it hooked up to it and see what kind of power im actually making. but dyno's are not a common shop tool in my area so ill keep my fingers crossed.