Busch got by Allgaier on Lap 160 of 188 while the two were racing hard for the lead and Busch then was able to successfully fend off Allgaier on three more restarts.
The victory in the Tennessee Lottery 250 was the 100th of Busch’s Xfinity career. He was already the series’ all-time wins leader.
“I remember growing up as a kid and watching Mark Martin win every week, you know, in that No. 60 car. You just look at the domination that he had,” Busch said.
“Just phenomenal years of being able to have such an association with Joe Gibbs Racing and Toyota. It’s so cool to have M&Ms on board for my 100th win here in the Xfinity Series. They’ve been my longest and best and best sports sponsor there is in my opinion.
“I want to give a shoutout to Rowdy Nation. I saw a lot of stand up with Allgaier took the lead and a lot of you sat back down when I took the lead. Pretty awesome day.”
Asked what he would do with the Gibson guitar awarded to the race winners at Nashville, Busch quipped, “Everybody’s getting a piece tonight!”
Harrison Burton finished third, Josh Berry was fourth and A.J. Allmendinger rounded out the top-five.
“Running second sucks. When we took the lead from Kyle, I thought we were good,” Allgaier said after the race.
Completing the top-10 were Brandon Jones, Jeb Burton, Noah Gragson, Austin Hill and Riley Herbst.
Following the break between Stages 2 and 3, most of the lead-lap drivers pit but Gragson stayed out and inherited the lead.
On the restart on Lap 97, Gragson was followed by Busch, Daniel Hemric and Harrison Burton.
Busch quickly got around Gragson to reclaim the lead on the restart.
On Lap 141, Brandon Brown had a right-front tire go down, which did damage to his suspension and required a trip to the garage.
All lead-lap cars pit with Busch the first off pit road. On the restart on Lap 149, Busch was followed by Allgaier, Jones and Hemric.
After racing side-by-side with Busch for two laps, Allgaier finally cleared him for the lead on Lap 151.
On Lap 155, Jade Buford got into Joe Graf Jr. and both ended up wrecked off Turn 4 to bring out a caution.
When the race returned to green on Lap 160, Allgaier led the way followed by Busch, Hemric and Michael Annett.
As the Kyle Busch and Allgaier came off Turn 4 racing side-by-side after the restart, Annett got up and into Hemric, which triggered a multi-car accident that also collected Austin Cindric.
The race returned to green on Lap 169 with Busch out front followed by Allgaier and Jones.
Ryan Sieg spun off Turn 4 and made slight contact with Gragson and Justin Haley, which brought out the seventh caution of the race.
A handful of cars elected to pit, but Busch remained on the track and in the lead on the restart with nine laps remaining.
After contact from Ryan Sieg, Landon Cassill spun and hit the wall on Lap 182 to bring out another caution.
The race returned in overtime with Busch still in command followed by Allgaier, Jones and Harrison Burton.
Busch regained command of the race and held off Allgaier to claim the win in Stage 2.
Hemric was third, Harrison Burton fourth and Annett rounded out the top-five.
Following the break between Stages 1 and 2, all lead-lap cars pit with Cindric the first off pit road. Allmendinger was penalized during his pit stop for not entering pit road single-file and had to restart from the rear of the field.
On the restart on Lap 54, Cindric was followed by Busch, Hemric and Jones.
Busch powered around Cindric to retake the lead on the restart in Turn 1.
On Lap 70, Stefan Parsons wrecked on the frontstretch after contact with David Starr to bring out a caution.
Several drivers pit but Busch remained on the track and in the lead when the race returned to green on Lap 76.
With five laps to go, Busch had moved out to a 2.7-second lead over Allgaier with Hemric in third.
Cindric led every lap and easily held off Busch to take the Stage 1 win.
Hemric was third, Harrison Burton was fourth and Allgaier rounded out the top-five.
Busch started on the pole but Cindric got around him off Turn 4 to lead the first lap.
With 25 laps remaining in the first stage, Cindric held a 1.6-second lead over Busch as Harrison Burton ran third.
With 10 to go, Cindric’s lead over Busch had grown to more than 2 seconds.