Sofio made only one start in the 2004 Atlantic Championship at Long Beach, finishing 12th overall and winning the C2-class. For the remainder of the season, he worked as a mechanic for Cam Binder Racing.[2]
In 2005, Sofio won the C2-class again at Long Beach finishing fifth overall. After Long Beach, Sofio joined Mathiasen Motorsports for the remainder of the season.[2] Sofio won six more races in the C2-class en route to the C2 Cup championship.[3][4]
Sofio returned with Mathiasen Motorsports for 2006.[1] On top of driving, Sofio was the chief engineer, general manager, and truck driver for the team until 2007. Sofio finished a career-high 11th in the overall championship.[5]
