Those numbers are a bit of a stretch. Looking at the flow data for the M62
and the power consumption
366whp is basically unbelievable from a M62 supercharger. The supercharger is off the map, but even if you were to take the numbers for 14k rpm at 440cfm(and at 11psi it will be less efficient than at 10psi), relate it directly to 21k rpm(1MZ crank pulley is 6.2", supercharger pulley I assume is 2", which makes for a supercharger spinning at 21k and change at the 1MZ's redline of 6800rpm) and say the supercharger is flowing 660cfm(of very hot air judging by the temperature graph):
We don't have all the data necessary to do an accurate representation, but 660cfm(and that's assuming the supercharger flows as efficiently that far off the map), of very hot air, minus the 56 hp it's going to take to drive the supercharger that hard, minus drivetrain loss...
A common rule of thumb is 150 cfm is good for 100hp, so 660 cfm will be 435hp. Minus the 56hp to spin the supercharger, 379hp. That leaves all of 13hp for drivetrain loss.
Or look at it from the other direction, 56hp to drive the supercharger, even being very liberal with drivetrain loss of 15%, do you believe a M62 supercharger is capable of making 475 hp? 366 x 1.15 = 420 + 56 = 475 at the crank.
I've also seen a car lose 20% going from Churchs to a Dynojet(no, not same day, but that's still more variance than most dynos will see).
go go gadget flame suit