surge/hesitation when accelerating

Hi, wouldnt if i can get some advice
i have a bugeye wrx, which has a surge/hesitation when accelerating in the 3.5-4.5k rpm stage
any ideas?
i tried to reset the ECU (battery disconnect for 4 hrs and pushing of brakes to drain - hope its the right way)
and have checked the airflow sensor on the air intake
please help!

Could be any number of things mate, depending on mods done etc.

Probably best to get the diagnostics computer on to it to be sure, sure ask the traders on here, they have the subaru equipment and can sort you out no bother.

As above!
Dan