My 09 did the same thing on the dyno. I was at McNews getting a N2o set up tuned at the time. Ray was able to tune the issue out. He said he had the same prob with a few stangs. If you have problems fixing the issue I would suggest emailing or calling Ray at McNews and talking to him about it.
FR '11 FF Mod pick
FR '12 Carlisle Nifty Fifty Award/Best in Boost/Best 08-11/Finest 5 Pick
FR '13 Carlisle 1st Place Award 08-11 Focus/1st place 08-11 Focus (FR13 award)/FSWerks pick/Ford Racing pick/Finest 5 pick/Top pick in the finest 5