DOVER, Del. (AP) -- Kyle Busch would like to believe he would have defeated Jimmie Johnson even without the four-time champion making a rare pit road mistake.
Busch never will know, and he doesn't really care.
When Johnson was penalized for speeding on the final pit stop, that was all the opportunity Busch needed to pull away late Sunday and win his second race in two days at Dover International Speedway.
Johnson made a quick burst out of the box and accelerated trying to catch a departing Busch coming off pit road. Busch joked that he wanted to "coax him into speeding a little bit."
"I don't know if that happened or not, but I'm going to say it did," Busch said.
Busch's victory capped a wildly successful weekend for the Joe Gibbs Racing driver.
Busch missed the tripleheader sweep on the one-mile concrete track by just a couple gallons of gas.
He was in position to win the Trucks Series race on Friday but ran out of gas at the end. He easily took the checkered flag in Saturday's second-tier series race and raced about 800 miles in three days.
"It's not going to hurt my feelings too bad to go to bed tonight and know that I lost Friday," Busch said. "I'm going to think more about today."
On Sunday, Busch swapped the lead with Johnson throughout most of the 400-mile race run in front of thousands of empty seats. He expected the duel to continue until Johnson was clocked at 40.09 mph in a 35 mph zone.
"I just had too much forward bite leaving the pit box and got going too fast and got busted," Johnson said.
Busch was sorry he was denied an epic late-race showdown.
"Unfortunately for those guys, they got busted for speeding and we weren't able to beat them outright and race them around the end of the race," Busch said. "I'm going on a limb to say we could beat them today with or without the penalty."
Johnson, who won both Dover races last year, finished 16th after having the dominant car most of the race. Johnson led 225 laps to Busch's 131.
"I ran my guts out trying to pass him," Johnson said. "It's unfortunate we didn't have a chance there at the end."
Jeff Burton was second and Matt Kenseth third. Denny Hamlin and David Reutimann rounded out the top five.
Johnson recorded DNF's in two of his last three races and gave other drivers a feeling that he may finally be vulnerable.
Kenseth said it was too early to count out Johnson.
"It looked like he was going to win today," he said.
Busch won his second race of the season -- he won at Richmond International Raceway two weeks ago -- and moved into second place in the standings behind seventh-place finisher Kevin Harvick.
Joe Gibbs Racing has been putting pressure on Johnson's four-year reign atop the standings. JGR drivers Busch and Hamlin have been two of the hottest drivers over Johnson's seven-race winless stretch and expect to contend for the title over the final 10 races.
"We're just getting started really here," owner Joe Gibbs said. "I'm thrilled that the last seven or eight weeks have gone so well for us, but the reality is, that can all turn in a week."
Busch became the second driver to win the Cup and Nationwide races in the same weekend at Dover. Harry Gant did it in September 1991.
Johnson led eight times and Busch six as two of the elite drivers in the sport engaged in back-and-forth action at various times of the race.
"We've been working real hard at just keeping my head in the game more, and it seems to be working a little bit, too," Busch said.
Busch overcame early radio issues in the No. 18 Toyota. He couldn't hear his crew and told them to stand on the wall and wave if they could hear him. The crew waved back.
Busch heard nothing for about 30 laps until suddenly the voice of his crew chief talking to his spotter about how NASCAR was going to pull the No. 18 off to fix the problem came through loud and clear.
"I'm like, 'Oh no they're not. Here I am," Busch said.
When Johnson was hit for speeding, team members high-fived and briefly celebrated in the pits.
Johnson lost the lead for good with 38 laps left and Busch led the final 35 laps.
"It was a fun battle there racing him for the last 100 laps or so we had," together, Busch said.