Faster versions of the S550 were incoming, but the fact that the Mustang GT now lived up to its Grand ... (and a limited run for 2015) , among other upgrades that largely kept the S550's comfort ...

Higher trim levels offered more features, and the S550 received upgrades or new features throughout ... the charisma and performance that Mustang GT fans demand. All powertrains were available ...

Responding to this situation, Ford chose to offer an efficient EcoBoost four-banger in the S550 ... upgrades, especially the engine recalibration kit. If you’ve got a four-cylinder Mustang ...