The TSB is just a $5 o-ring on the crank position sensor that plugs in to the rear end of the engine block. Its stupid of the dealer to refuse to do it - its 15 minutes of labor for the tech to replace the o-ring and a few more minutes to do a re-learn.
Agreed on this. I had a similar problem at 1,100 miles. Not only did the TSB make the misfire issue go away, but also smoothed out the car's tendency to lurch soon after start up with slight throttle tip-in.
Black 2013 Mustang 5.0 MT82 w/401A package and 3.31s
Black 2000 Mustang GT (owned 2001-2013, sold at 177,000 miles)
Brown 1971 Triumph TR6