Victories over Inter Turku and KuPS in their last three matches had given AC Oulu renewed hope of qualifying for Europe, especially as the side they were chasing, Gnistan, had lost their last two and were winless in four.
The goal-fest began in the fifth minute, when Mikko Pitkanen headed in a Rasmus Karjalainen corner to give Oulu the lead, but Gnistan goalkeeper Otso Virtanen should have done better with his attempt to save. Five minutes later, the visitors had another corner and again Karjalainen's delivery was on the money, flicked in at the near post by the head of Iiro Mendolin.
Midway through the first half Gnistan were back in it when a half-clearance was met by a sweet first-time Sergei Eremenko strike from 25 yards which arrowed into the bottom corner, but a half to remember for Karjalainen continued when he followed up his own saved shot to turn home the rebound just before the break.
The home side were back to within one six minutes after the break when Adam Jouhi played a one-two with Saku Ylatupa and guided home the finish, yet five minutes from time Oulu finally sealed the points when Roope Riski sent Lamine Ghezali away and clear following a Gnistan corner, and his effort squeezed under Virtanen for 4-2.
Jouhi curled a beautiful strike into the top corner from range in added time, but that was no more than a consolation for Gnistan, who are overtaken by Oulu in the table with three matches still to play.
Inter Turku did enough to go five points clear of both HJK and KuPS before the two challengers meet in Helsinki on Sunday 25th, returning to winning ways after defeat to Oulu, while VPS stay bottom of the Championship Group following successive defeats.
The first half was extended following a nasty clash of heads between VPS' Yassin Daoussi and FC Inter goalkeeper Eetu Huuhtonen, with the former having to be substituted, and in the lengthy period of added time, the visitors came closest to going ahead through an Alie Conteh header which dropped a whisker wide.
Inter Turku tested Mamadou Jalloh in the VPS goal plenty of times in the second half but the breakthrough didn't appear forthcoming, especially after Janne-Pekka Laine received a second yellow card for a pull back right under the nose of the referee with 13 minutes to play.
But in the 84th minute, the 10 men found a way through, when Lauri Laine collected Eeli Kiiskila's pass on the left, cut inside and drilled a shot past Jalloh and into the opposite corner to take all three points.
It's a crucial win for the Turku side ahead of their meeting with HJK next time out, while the Vaasa side are now four points off the European places.