Simplify the following text for a Grade 7 native English-speaking person.
Original: Shirov became the World Champion ( under 16 ) in 1988 , the World Under-20 Vice-Champion in 1990 ( second on tiebreaks to Ilya Gurevich ) , and achieved the title of Grandmaster in 1990 .
Simplified: Shirov became the World Champion ( under 16 ) in 1988 , and achieved the title of grandmaster in 1990 .