Muncie finished the 1980 season strong with 659 Yards in 11 Games, but he would have the most productive season of his career in 1981.  Under the guidance of Chargers, Head Coach, Don Coryell, Muncie was a large part of his offense.  Muncie had 1,506 Yards From Scrimmage with a league-leading 19 Touchdowns, and he went to his second Pro Bowl.  In the strike-shortened 1982 campaign, Muncie was again chosen for the Pro Bowl, and the year after, he had 13 TDs and 1,282 YFS. 

Muncie's cocaine use caught up with him, and the Chargers looked to get rid of him.  They tried to trade him to Miami early in the 1984 season, but the transaction was voided when he flunked a drug test.  He was released by San Diego and suspended by the NFL, and he never played in the NFL again.

While Muncie's professional career was over, he still left the Chargers with 4,546 Yards from Scrimmage and 45 Touchdowns, which was impressive for only 51 games.