For sure my early build 2014 Mustang GT has a Boss ECU. PN DR3A-12A650 ACD. The 2013 Boss used DR3A-12A650 ACC. The Interchange book says they are interchangeable. The last C might be for 2013 and the last D might be for 2014 if a Boss 2014 Mustang existed. With that info plus the fact that early build 2014 Mustang GTs with 6sp manual also can use the "Track Key System" that was offered maybe a month or so in March 2014 then discontinued. Then there has been a report that Boss Rods many be in early build 2014's. I just wonder if there is anyway of really telling if it's a Boss Long Block without taking the engine out of the car.
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