Sony Computer Entertainment's official Gran Turismo 2 web site has revealed that Gran Turismo 2 is not complete. In a FAQ section on the site, the developers commented that unfortunately due to time constraints they were unable to finish the game properly. Because of this, it is impossible for a player to complete more than 98.2 percent.
Sony Computer Entertainment America had no comment on the matter, but it's likely the remaining 1.8 percent lies in the missing drag racing course.