New York traded Wagner to Boston on Aug. 25 for two players to be named.
Carter batted .294 with 16 home runs and 61 RBIs in 116 games with Triple-A Pawtucket this season. The 26-year-old outfielder was added to the Mets' 40-man roster Wednesday.
Carter was hitless in five at-bats for the Red Sox in April. He is a .306 career hitter with 126 homers in 726 minor league games.
Lora, a 20-year-old first baseman, batted .222 with three homers and seven RBIs in 34 games with the rookie-level Gulf Coast Red Sox this season.