Welcome to FTE. Go get that code checked from somewhere that knows what they are doing. Advance doesnt have the tools needed to scan a Powerstroke. Look for a buddy that has a program or tool like a snap-on scanner, or Autoenginuity. Or a buddy with something like a superchips or diablo tuner, that can pull codes for you. I'm betting it is something like the Injection Pressure Regulator valve sticking when you are easing into the pedal, when it sticks a little more closed than it should be, causing more fuel to be given, giving the surging feeling. The turbo has nothing to do with it, wastegate whatever, it only spools up and lets off for a little bit because it is being fed more fuel (energy to spool it). Im betting you have some code that is P12xx.