Jordan Cohen missed, but then Gray and Tyler Nicoll-Hylton converted to make sure the team reached their goal of making the top four.
"It was pretty tense, to be frank," said Spence yesterday.
"I did think of that tournament last year, but I think the character got them through. "We put a lot of pressure on, right to the end.
"Our boys dominated the game. As I say that, I think they panicked under the pressure, we're playing better teams now."
The squad was guilty of trying to beat their markers as opposed to putting on the sweeping passing chains they had practised, but with time running out they found the way for Gray to score the equaliser.
Wanganui will now meet Horowhenua in today's semifinals, after they got home with two goals in the final quarter to beat North Harbour 2-1.
Spence said his team beat Horowhenua 4-0 at a mini-tournament in the build-up to the championships. However they had improved since. In pool play, Horowhenua beat Canterbury 6-1, Northland 5-2, and Southland 4-1. "Whomever wins tomorrow's game, I'd be pretty confident to say they'll win the tournament," Spence said.