Jimmy,
This is the same formula I was referring to, PSI/14.7 is a quick way of converting to BAR, you add 1 BAR to account for the atmosphere, and multiply the total intake pressure (atmosphere + generated boost pressure) by the car's NA output to obtain its theoretical power level.
All things being equal this should provide an accurate number, assuming similar dyno conditions, and an accurate boost reading. For instance, prior to my last tune my HP turbo nsx was producing 383rwhp at 0.55 bar (8psi) - the theoretical value provided by this formula for 0.55 bar is 387.5rwhp, so my true power was close to the theoretical value.
The last time I had the car tuned, perhaps a month ago, we disabled the VVIS system, and advanced timing slightly to offset the low end loss this resulted in; the resulting power level was 418.8rwhp, but we also noticed boost creep up to a peak of 0.6 bar, or 8.7 psi. Using the formula for 0.6 bar we see a theoretical value of 400rwhp, but this formula doesn't take into account the increased timing, or the disabling of the VVIS system. When we ran the old map with the only change being the disabled VVIS we found a +20rwhp peak gain, and when we adjusted timing we didn't see much change in the peak value, only a nice bump in midrange values - so, if we have a theoretical value of 400rwhp, and an increase of +20rwhp from the VVIS system being disabled, we have a theoretical value of 420rwhp, compared to my actual value of 418.8rwhp - it seems to be rather accurate.
If Craig's nsx produced 222rwhp in stock form on your dyno, how was he able to produce 605rwhp at *only* 1.07 bar? This is triple the power with an increase of only 1 atm; it just doesn't make sense unless you have a very aggressive tune, and more than 15.5psi of boost. Craig also made a post last month where he said his car makes 474rwhp on his 'street' tune of 8.8 psi - this is almost the exact same boost level I have, with the same stock 3.0L engine, the same turbo kit piping, the same disabled VVIS system, and the same diameter turbo, yet I have 418.8rwhp, and he says his car has 474rwhp - is this the result of timing, boost creep, or something else? When I showed Craig's earlier thread to my tuner he could not explain the resulting numbers, at that boost level.