A photo would help A bunch.
To remove A warp with A heat gun you sometimes need help, an extra set of hands come in handy. The part with A warp is twisted just past being straight and you will notice the sag in the covering on the bottom/side, with the heat gun you tighten this up and hold the part until the covering is cooled.
Sometimes it takes A couple of tries, sometimes the warp comes back on A hot day and the plane is out in the sun. You just do it again.
All you are doing is drawing the wrped part straight by shrinking the covering.