I'm new to the website. I joined to ask a few questions. I have a 2003 Subaru WRX with an automatic transmission. I'm getting hesitation/surging under heavy acceleration. Usually at high speeds. Idle's fine, runs fine. She only has 50,000 miles on her. No check engine lights.
Everything is factory on the car except a K&N filter. Subaru dealer didn't find anything wrong with it, but I don't know if they took it up to 80mph +. All fluids have been checked and are fine. I take very good care of my car and don't beat on it.
Also I'm looking for the best and cheapest way to make the car faster without modifications leading to loss of gas mileage.
Any help would be appreciated.