For the second time already this season, nine goals have been scored in one Allsvenskan game, but unlike Hammarby's 8-1 win over Orgryte, this one couldn't have been closer, though for Goteborg - who are now three unbeaten - it probably shouldn't have been.
The opener arrived after just 13 seconds - Noah Tolf sent a long ball forward down the left, which Tobias Heintz chased as he got in behind the defence far too easily before slotting home. And it took Heintz another seven minutes to add his second, volleying in from close range after Sebastian Clemmensen's header across goal.
Amazingly, Goteborg were three up after nine minutes, as another hopeful ball over the top allowed a forward to get in behind - this time it was Rockson Yeboah to Adam Bergmark-Wiberg, who let the ball bounce up before catching it sweetly and arrowing it into the bottom corner.
The home side finally weathered the storm before creating one of their own with two goals in three minutes just before the half-hour mark. Simon Gefvert squared the ball across the area from the right for Karl Gunnarsson to apply a cool finish, before a Marcus Baggesen corner was squeezed in at the near post by Mikkel Ladefoged's header.
Vasteras' hard work to get back into the game looked to have come undone 37 minutes in, when Bergmark-Wiberg played the ball in low, and it was swept in at the far post by Heintz, completing an outstanding hat-trick.
But after the break, Vasteras showed they weren't done yet, as in the 53rd minute, Gunnarsson attacked through the centre before slipping the ball through for Taonsa Axel, who finished to make it 4-3.
Incredibly, the match was level at the midway point in the second half, as Vasteras worked the ball into the area from the left, before Jens Magnusson squared to Axel, who once again kept his cool in front of goal to complete his brace.
However, 11 minutes from time, it was IFK who won it, as Heintz scored his fourth of an extraordinary game. A free-kick played into the area was hooked clear to the Norwegian 25 yards out, and he took it down and unleashed a curling effort that sailed around the goalkeeper and inside the far post.
A goal worthy of winning any match was not enough to take Goteborg out of the bottom three, but only goal difference is now keeping them there. As for Vasteras, they sit 11th after their two-game unbeaten run was ended.
It's as you were at the top of the table, with Sirius leading the standings by eight points ahead of Hacken, who needed to come from two goals down to beat Hammarby and ensure they didn't lose further ground on the leaders.
The visitors came into this on a two-game winning streak, and that looked sure to end after Victor Lind collected Paulos Abraham's pass, cut inside and powered in a strike from 20 yards in the ninth minute, before putting Bajen 2-0 up half an hour later when hammering in another shot from the edge of the box following a poor clearance.
However, the match completely swung early in the second half, when Victor Eriksson pulled back Silas Andersen inside the box and Amor Layouni dispatched the resulting penalty. With 10 minutes of the second period played, the Hammarby lead was wiped out, as Andersen weaved his way past defenders through the middle of the visitors' half before steering the ball into the bottom corner.
And the turnaround was complete 11 minutes from time, when the alert Adrian Svanback beat the Hammarby defence to Julius Lindberg's cutback, and there was no stopping his finish from the edge of the six-yard box.
Hacken now have five wins and five draws from their 10 games so far, while Hammarby have dropped to fourth this weekend after this latest defeat.
There was another home comeback in Degerfors, where the hosts dug deep to earn a point against Brommapojkarna. There was also an early goal in this one - BP went ahead in just the second minute through Mads Hansen, before Simon Strand doubled the advantage seven minutes into the second half.
Four minutes later, Strand turned from hero to zero as his own goal allowed the home side back into it, and by the 63rd minute Degerfors had levelled things up again through Marcus Rafferty.
The point ends a run of two successive wins for the Bromma Boys, who sit seventh but just three points off the European places. 12th-placed Degerfors are now winless in six, but four of those have been drawn.
Allsvenskan now goes on its midseason break, returning on 3rd July.
Review the first part of the Allsvenskan season on Flashscore.