Have you twisted the torque fin to the opposite direction?
Good point. Since we know nothing of the setup, we have no clue if anyone ever set the tab anywhere remotely near what it might need to be.
Additionally, the OP did not point out that he had stick steering! The NFB system I referred him to is for systems with a steering wheel! It is not usable with a stick steering system.
To the OP: If your engine was set too low on the transom when mounted, it will steer like a stiff truck with no power steering. What matters is where the anti-cavitation plate is located with respect to the bottom of the hull when the plate is parallel to the bottom of the hull. If it is several inches below the bottom of the hull, I'm going to guess that's part of your problem. If it is close to even, then that probably isn't a problem. I can't advise exactly where it should be set for you because I don't have experience with your model boat.
Do you have tilt/trim on your engine? If you don't it should be set at about perpendicular when the boat is running on plane. Not to be rude, but if you have tilt/trim, do you know how it should be used? (This can affect steering performance.)