Yes, they have been retuned-- all of them. I previously thought they were just rebadged, but after speaking with Andy about the nature of the internal changes (air pressure, recalibration, efficiency) and then A/Bing Bravo : FXA, I stand corrected. What I can say about them is that the FXA re-iterations of the Bravo series amount to the kind of changes that would have earned a separate designation on the older AS(G)x models (ASG1, 1b, 1+, 1.5, 2, 2.5) and thereby are more significant than I would have given credit for. After listening to the FXAs, my opinion is that they are 'prettier' in presentation, particularly between 1000-3000hz.
Much respect~