By TOM WITHERS
Tuesday, May 13, 2008 7:45 AM
CLEVELAND - Back to even, and back to Boston _ with authority. LeBron James scored 21 points, jamming in a powerhouse dunk over a defenseless Kevin Garnett in the final two minutes, as the Cleveland Cavaliers beat the homesick Celtics 88-77 in Game 4 on Monday night to tie the best-of-seven series at 2-2.