Enfinger was among several trucks that pit for new tires under a late race caution and he had made his way up to fourth when the race went into overtime.
John Hunter Nemechek led on the restart but was quickly passed by Zane Smith but Enfinger moved past them both at the start of the final lap and held off Ben Rhodes by 0.477 seconds to seal the win.
With the victory, Enfinger automatically advances to Round 2 of the playoffs regardless of his performance in the next two races. The win is the seventh of his career.
“We’re finally moving forward. This is the first laps we’ve led since Atlanta or something like that,” Enfinger said. “We’ve been terrible all season. We’ve just been off a little bit as an organization.
“We’ve been working so hard because we’ve been sucking. It hurts to say it, but we have had a terrible season to this point. But we had a great No. 23 Chevy all night. I felt like every time we got the lead, a caution came out.
“It was a pretty special night. I’m definitely very, very thankful.”
Regular season champion Zane Smith ended up third, Stewart Friesen was fourth and Corey Heim rounded out the top-five.
Completing the top-10 were Tyler Ankrum, Lane Riggs, Ty Majeski, Matt Crafton and Nemechek.
Following the break between Stages 2 and 3, only a handful of trucks elected to pit. Majeski remained on the track and in the lead when the race returned to green on Lap 129.
NASCAR displayed a caution on Lap 140 for debris on the track. Majeski remained in the lead on the restart on Lap 146.
Zane Smith was involved in a wreck with Lawless Alan on Lap 148 as the field raced four-wide.
Most of the lead-lap trucks remained on the track. Majeski continued to lead on the restart on Lap 159 followed by Enfinger and Nemechek.
With 30 laps remaining, Majeski had opened up a 1.7-second lead over Enfinger as Nemechek ran third and Friesen fourth.
With 15 laps to go, Enfinger closed to within 1.3 seconds of Majeski but was making little progress against the race leader.
After the two ran up on some lapped traffic, Enfinger caught Majeski and reclaimed the lead on Lap 189.
Colby Howard wrecked on Lap 191 after contact with Hocevar in Turn 1 to bring out the ninth caution of the race.
Most of the lead-lap trucks pit with Majeski the first off pit road. Nemechek and nine others elected to stay out.
The race resumed with two laps to go with Nemechek in the lead followed by Taylor Gray, Ankrum and Zane Smith. Majeski…