Complex sentence: Four years of F1 racing for underfunded teams led him to seek a new challenge, and thus he took a year out and competed in the 1988 World Sportscar Championship and won the world sports car title, with a record points haul.
Split into simpler sentences: Four years of F1 racing for underfunded teams led him to seek a new challenge, and thus he took a year out and competed in the 1988 World Sportscar Championship. He won his world sports car title, with a record points haul.