The Sang et Or picked up only one point from their first five matches in Ligue 1, but a hard-fought 1-1 draw at Sevilla in their Group B opener served as a trigger.
They followed up with two wins against Toulouse and RC Strasbourg and striker Wahi, who joined from Montpellier during the close season to replace Lois Openda after the Belgium striker left for RB Leipzig, scored his first goal.
He had showed glimpses of his huge talent in Sevilla and on Tuesday, the forward delivered a scintillating performance, setting up Adrien Thomasson for the equaliser and netting the winner in the 69th minute.
"I was telling you that he was on the right path. He got there a month and a half ago and he's been making big strides," coach Franck Haise said.
"He scored the winner in Strasbourg last Friday and he scored the winner again tonight. He is showing that he is a high-quality striker."
"I'm starting to find my marks with my teammates. I knew where he (Przemyslaw Frankowski) would cross," Wahi said of his goal.
Wahi was helped by a side who rediscovered their touch, playing as a compact block and hurting their opponents on the wings.
"We can say that the Sevilla game was a turning point. We've found our mark again and we are again a team who are hard to play against," midfielder Thomasson said.
While Arsenal coach Mikel Arteta lamented his side's lack of efficacy in both boxes, Lens's best two players on the pitch were Wahi and goalkeeper Brice Samba.
Samba made several superb stops, including a handball-style save with his foot to deny Takehiro Tomiyasu to cap a remarkable performance.
The result put Lens top of Group B with four points, one ahead of Arsenal with Sevilla in third place on two points after they drew 2-2 with PSV Eindhoven (1) in the Netherlands.
On Tuesday night, the official Ligue 1 X (ex-Twitter) account wrote: "Farmers League strikes again", but Lens kept their feet on the ground well aware that the campaign is just starting.
They will also remember that in their last Champions League participation, they were knocked out in the group stage despite registering eight points in a group that featured Bayern Munich and AC Milan.
"We're the minnows of this group, let us be," Samba said.
