For the FXT, it is unlikely that this will fix the problem of hesitation, this problem is only evident in 08+WRX's and STI's. It is much worse with the STI's. With The WRX you just get wide fuel trims but very little hesitation. For the most part the WRX hesitations were fixed by the per injector pulsewidth compensation tables from the factory.
You can also use this spreadsheet to change the per injector pulsewidth compensation tables as well.
For the earlier cars without this issue. You can use this technique to create a more stable maf scale and minimize and stabilize AF Learning.
I wish we could truly find the cause of this. We only have a few band-aid fixes, by forcing the car to add fuel when it shouldn't need to. When you upgrade injectors on STI's this gets out of hand. I have tuned cars with fuel rails and aftermarket fpr's, Changed the Fuel Pump Duties. Altered the dual AVCS tables in every direction. The problem always persists.