Hmmm. I'm slightly skeptical but I won't call BS. Whats the elevation where this took place?
If you were making 16# then the numbers sound about right. You essentially have a Boss engine in terms of the heads and intake with more agressive cams. That could put you over 450rwhp pretty easily and maybe even 500rwhp in n/a trim. In a perfect world you will double your n/a power output at double atmospheric pressure(14.7psi) so if you are making 450rwhp and are pullied to make 16# then your numbers sound right on the money. Considering you are getting signs that you are maxing out that little P1........I can see this being legit. ****ing awesome. Please keep us posted on how long the stock bottom holds that much power.
There is a member on here's 11 5.0 who sprayed a 100 shot, then a 150, then a 200, shifting at 7500 or so, even sprayed it in 6th before, has made multiple back to back to back to back pulls, etc. He then put a blower on it making 627 rwhp, then retuned/swapped exhausts, now up to 688 rwhp, with some extended umm "top speed" runs in 6th, having thrown the belt, overheated etc, AND ITS STILL F@CKING RUNNING!