Only one S550 Mustang can be the world’s quickest, and it's Bart Tobener's DiabloSport 2015 Mustang GT, powered by a turbocharged Coyote 5.0 with a Holley Dominator EFI ECU and a brand-new Holley EFI Sniper fabricated intake. Tobener ripped up the Lucas Oil Raceway in Indianapolis earlier this year with the first seven-second run for the new S550 platform, a 7.99 at 171 mph. "This thing will run in the low 7.60s when we get a few issues figured out," said "Bad Bart," who obliterated those historic marks with a subsequent 7.92 at nearly 175 at Route 66 Raceway in Chicago. "We really didn't get as many hits at the track as we wanted to after we got into the sevens because so many races were affected by rain." Tobener used the big showdown last weekend at No Mercy 7 at South Georgia Motorsports Park as a test session. Running a smaller turbo and the same rear-end gear he would on a quarter-mile track, Tobener still managed to go a few rounds in Ultra Street eliminations despite not being set up for eighth-mile competition. Instead of his usual billet-wheel 76mm turbo, he had a cast 76mm wheel to comply with series rules that made the car, as he put it, "feel slow." Making about 120 horsepower less than he usually does, Tobener recorded a best of 5.09 seconds on the eighth-mile course, which compares favorably to his seven-second blasts down the full quarter-mile. "The eighth-mile time on that 7.92 earlier this year was a 5.14, so we picked up half a tenth," Tobener said. "Who knows how much quicker that would have been in to the quarter-mile, and this was one time we weren't really trying to win – we just wanted to run on a good track and see where we were at." Batting problems with his transmission, converter, shocks, and anti-roll bar in infrequent appearances this season, Tobener's turbocharged beast actually got in only eight representative runs after his amazing start. "Some of it is just the new-car stuff you're always going to deal with," said Tobener, who just switched to an all-new turbocharged combination this year. "For leaving the car in quarter-mile trim and running a smaller turbo, I'd say it ran pretty good. The main thing was to see if we had our issues fixed, and we did. I know it'll go low 7.60s at about 186 mph the way it is, and it needs to be in the 7.40s to win next year." Check out a complete gallery of photos on Tobener's history-making S550 here.