Nope, It's Cancelled:

Posted: Wed 25 Feb 2004

Earlier today it was reported that the Wanganui SX was Postponed:

Now MNZ are advising that the fourth and final round of the National Supercross scheduled for this weekend at Cooks Gardens has been cancelled.

It has also been reported that the Wanganui Club will refund rider entries over the next week and that the final placings for the now three round series will be confirmed soon.
They will most probably be as per this - Report: