Not sure about your "method" but I just did a little simple math .

Stock STI = 215-220whp on my road dyno
So 300/220 = 1.364 which is our correction factor to get back to crank hp.

So 325whp * 1.364 = 443bhp


Now, on a Dynojet a stock sti puts down ~250whp.
So 250/220 = 1.1364 is our correction factor to go from my road dyno to dynojet numbers

So 325 * 1.1364 = 370whp


This is a little voodoo math but in general it does work to convert numbers from one dyno to another assuming you have good reference points.

Thanks