The Tonga international was awarded a try three minutes from time by the video referee and Luke Gale kicked the conversion to end a two-game losing streak for Hull after it looked as though the Wolves had clinched victory with a Matty Ashton try with seven minutes to play.
It was a big win for the Black and Whites - after an underwhelming derby defeat to Hull KR on Good Friday - against a Wire side buoyed by a big win over Salford last time out.
After both sides traded early field position, Hull scored first against a 12-man Wolves.
Shortly after Ben Currie was sin binned for pulling back Jordan Lane in a try scoring position, Jamie Shaul finished off a flowing move from right to left.
The Wolves bit back shortly after to level the scores as quick thinking from Daryl Clark caught the Hull defence napping and the hooker raced through off a penalty tap to score next to the posts.
The first half was end-to-end as the hosts went back in front through Brad Fash, who took a lovely short pass from Gale to touch down.
The Black and Whites started to exert some physical dominance, forcing Warrington to play out of their own half.
However, the hosts could not capitalise and conceded a try off a mistake to see the Wolves draw level once again.
Darnell McIntosh spilt a towering kick into the path of Ashton, who held off the cover defence to score his first in the corner, leaving the scores locked up at 12-12 at the break.
Both sides blew golden opportunities to score minutes into the second half, with Toby King intercepting a vital last pass from Shaul to stop Hull before the big centre’s final pass in space was knocked on at the other end.
The second half turned into a real arm wrestle with both sides looking for the crucial error to gain the upper hand.
It turned into a half of missed opportunities as both teams traded near misses, with neither seemingly able to land the killer blow. However, the final 10 minutes exploded into life.
Barely a minute after Gale had pulled a field goal attempt wide, the Wire went down the other end and took the lead for the first time, with Ashton taking Josh Thewlis’ lovely tip on to cross over out wide.
However, Hull had the final say and wrestled back the lead at the death through Ma’u’s converted try to earn the hosts a vital win.