ffs, VN S1 had a slightly different cam and a slightly different manifold to later versions, it had a tiny TINY!!!!! bit more power and a slight difference in the torque range then the 1.5s and the S2, same as the early S1 VN SS had more go then later on since Holden didn't quite know what they were doing to begin with since the Buick V6 was a last minute decision since they were originally going to put RB30s in the VN's till the Yen to AUD price went to ****.
The first V6s were more like the american FWD buicks at the time and they modded them slightly to suit there needs better once they had them selling and worked out the issues they were having to make them more reliable so they weren't fixing **** under warranty all the time.
The first 304s in the VN SS were guinea pigs and they changed the tune mapping slightly for the 1.5s and S2s, lowered the power slightly but made them more reliable.
This difference was only within the first 20 to 30,000 VNs from memory so around August to October/November 1988.
And yes i owned 1 in the first 10,000 build range so shut up since i do know about them.
And in no way would a stock VN V6 EVER!!!! Beat a Stock VL Turbo.