I read something to that affect in Sport Compact Car magazine. a guy wrote in asking how to build a high horsepower VG30E for his Z31. they said the 2-valve per cylinder head design would make it nearly impossible to get 300hp and he would have to bore it, run very high compression pistons, an un-streetable cam, and that he would be better off swapping in an RB.
considering you lose roughly 25% of your power through an automatic transmission 300/0.75 = 400 you would have to be making around 400hp at the crank if you are running an automatic transmission, which makes your claim very hard to believe considering the modifications mentioned. this means either the dyno you ran on was wrong, or you are lying.