Porsche made a comeback in the LMP2 category in 2005 with the new RS Spyder prototype, although this was run by closely associated customer teams rather than by the works. This was not welcomed very much, as rule makers intend the LMP1 category for factory entries, while the LMP2 should be reserved for privateers. Based on LMP2 regulations, the RS Spyder made its debut for Roger Penske's team at Mazda Raceway Laguna Seca during the final race of the 2005 American Le Mans Series season, and immediately garnered a class win in the LMP2 class and finishing 5th overall. The nimble albeit less powerful (due to the regulations) RS Spyder clearly possessed the pace to challenge Audi and Lola LMP1 cars in the ALMS. Penske Racing won the LMP2 championship on its first full season in 2006 and against Acura in 2007 and 2008. 2007 was the most successful year for the RS Spyder, winning 8 overall races and 11 class wins while the Audi R10 from the larger LMP1 class won only 4 overall victories. The car debuted on European circuits in 2008 and dominated the Le Mans Series; Van Merksteijn Motorsport, Team Essex and Horag Racing taking the first three places in the LMP2 championship. Van Merksteijn Motorsport took a class victory at the 2008 24 Hours of Le Mans and Team Essex won the LMP2 class at the 2009 24 Hours of Le Mans.