In 1999 Guerrero returned with Cobb Racing in the No. 50 Cobb Racing G-Force IR01-Nissan Infiniti Q45. Guerrero's best finish of the season was a 13th-place finish at the season-opening Transworld Diversified Services 200 at Walt Disney World Speedway. The team closed down following the Indianapolis 500 where Guerrero started and finished 25th. After Indianapolis Guerrero was ranked 17th in points. He eventually finished 30th in the championship with 36 points.