i agree that it could happen,, when i dynoed mine stock, i got a crazzy high number that was non sae corrected, it showed something similar to yours... i think it was a bit lower like 469 and 500..... im not sure how it showed those numbers but it did.. i thought i was king lol.. and then realized that something was up .. maybe it was that it was below 0 out in late fall and non sae around sea level.., not sure ..and i think it was a dyno jet which always read like 8% higher than a ture mustang dyno... so maybe add all those factors together and you get high readings.. who knows... but it still boils down to incorrect numbers no matter how you look at it... feels good until you realize somethings up and it cant be ture.. lol