gt2 0-1000 in 20.29
turbo 2 0-1000 in 20,37

we know that the turbo 2 pdk profits from his gearing over the gt2 specialy till about 200kmh.

But after 200kmh gt2 should be significantly faster than the 911 turbo

times messurerd 0-300kmh

gt2 33-36 sec
turbo 2 pdk 40-42 sec

So it could be likely the tested turbo had a bit more than 500hp than other wise the time differant 0-1000 should be bigger than 0.08 secs between gt2 and turbo.