You filled in 2004 Subaru WRX.
Please list Mileage and ALL mods pertaining to ECU Tuning, Power, and Drive-train. Suspension, cosmetic and audio modifications shouldn't be causing this kind of issue.
With that information we can better diagnose your issue.
You say it happens when you "hit the gas hard" do you have a tune? How long has this been happening? Did it happen before a certain modification? What ECU do you have? You said it was different?
Did you mean aftermarket ECU, or aftermarket tune?