Gunther had also started Saturday’s opening race in Indonesia from pole position, but showed far superior long-run pace in the second leg of the double header, converting pole into the lead then outduelling Andretti’s Jake Dennis to score his first FE win in three years.
A good getaway meant Gunther maintained his advantage into Turn 1, with Dennis also staying in second position despite Jaguar’s Mitch Evans making a rapid launch from third.
Gunther was the first of the frontrunners to activate the Attack Mode on lap four, dropping to third behind Dennis and Evans after rejoining the track.
Dennis followed Gunther into Attack Mode on the following tour and emerged in front, taking the net lead.
On lap 15, Dennis activated his second Attack Mode on the wider line at Turn 16, slipping momentarily behind both Gunther and Evans.
With Dennis stuck behind Evans, Gunther immediately upped his pace and set personal best times in sectors 1 and 2. As a result, when Gunther took his second Attack Mode on lap 17, he emerged back ahead of Dennis and reasserted his position at the front of the pack.
However, the battle for the lead was far from settled, with Dennis immediately putting the pressure on Gunther, as Evans remained first on the road and still with a chance of stealing the victory.
On lap 19, Dennis tried to go around the outside into Turn 1, a departure from the usual tactic of diving towards the inside into the right-hander.
The British driver managed to get his Andretti car ahead of Gunther’s Maserati but then had a twitchy moment at the corner exit, allowing the latter to come back and stay in the net lead of the race.
That would be as close Dennis would come to passing Gunther, with the German driver pulling out a two-second gap over the next seven laps.
He eventually took the chequered flag by 2.822s, scoring his first win since New York in 2021 with BMW as well as the first-ever for Maserati in FE following its takeover of the Venturi outfit for this season.
Dennis missed out on a second win of 2023 but extended his streak of podiums to four, while Evans completed the podium spots in third, albeit 18.5s behind Gunther after completely losing touch with the leading duo.
The two Nissans charged through the field in the closing stages of the race, with Sacha Fenestraz finishing fourth and team-mate Norman Nato ending up not far behind in fifth.
Their late race surge included an impressive move from Fenestraz on Stoffel Vandoorne into Turn 1, which left the DS Penske driver wide and also allowed Nato through. Nato then challenged Fenestraz, but ultimately settled for fifth.
Another driver to pass Vandoorne late on was race one winner Wehrlein, with the move allowing the Porsche driver to claim the lead of the championship by just one point over Dennis.
It followed overnight points leader Cassidy making an ambitious move over Wehrlein into Turn 16 that dropped him to the back of the pack.
Coming from a long way back into the left-hander, Envision driver Cassidy's front wing was clipped by Wehrlein's Porsche as they turned into the corner, leaving him stranded on track.
Although he was able to get going again, he could only recover to 18th at the finish, failing to score points for only the second time this season.
Seventh place in the race went to Wehrlein’s team-mate Antonio Felix da Costa, with Edoardo Mortara finishing eighth for Maserati after losing several places with a Turn 1 lock-up.
Vandoorne eventually finished a disappointing ninth, while Sebastien Buemi picked up the final championship point in 10th for Envision with a bold move over McLaren’s Rene Rast.
