Nomo (13-10) had just one win in his previous 11 starts, but apparently found some good karma in the park where he tossed a no-hitter on April 4. He allowed three runs and seven hits to improve to 3-0 against the Orioles this season.
The Japanese righthander fanned six and leads the American League with 220 strikeouts, 10 more than former Orioles righthanader Mike Mussina of the New York Yankees.
Boston trailed after six innings, 3-1, managing just three hits off Baltimore starter Calvin Maduro. But Maduro walked Morgan Burkhart to start the seventh and rookie Shea Hillenbrand singled with one out to chase the righthander.
Former Red Sox John Wasdin (1-1) came out of the bullpen and struck out rookie Angel Santos. But Stynes connected off a 1-1 offering to give Boston its first lead.
Doug Mirabelli added his 11th homer off rookie Willis Roberts in the ninth to give the Red Sox an insurance run.
Closer Ugueth Urbina allowed a run and two hits in the bottom of the ninth before striking out Jerry Hairston Jr. with the tying run in scoring position for his ninth save in 10 chances.
Orioles third baseman Cal Ripken began the final series of his storied career and ended a none-for-33 drought with a leadoff single in the fifth inning.