In the final minutes, Elfsborg had a ball in after a joint on a corner, but the goal was disallowed for offside.
The mess in connection with Berg's expulsion (see separate article) meant that extra time was set to seven minutes, where Elfsborg made it 3-1 in the 98th minute.
Noah Söderberg came on the left wing and got a good gap.
The IFK fans tried to pep up their decimated team but there was never really a good chance to equalise.
The goals came in the first half.
In Elfsborg's 2-1 goal, Per Frick shot from a shot that Warner Hahn saved with difficulty.
He then reached for the ball which curled towards his own goal line and slammed it into his own goal - hard courted by Alexander Bernhardsson who completed it right over the goal line.
- It is clear that I will take it if I get it, Bernhardsson said with a smile to Discovery + during the break.
Bernardsson's prayers were heard and he officially got the goal.
At 1-1, red-hot Michael Baidoo moved laterally and found the gap past Warner Hahn.
Gothenburg took the lead when veteran Gustav Svensson held on at the far post and headed in 1-0 – the 35-year-old's first Allsvenskan goal since 2015.