Are you sure you don't have ripped seat foam. If you have a 86 or later car the seatbacks have a vertical metal side bolsters that the older seats did not have. Typically the thin seatfoam over the inside bolster splits and makes it look like the seat is tilting toward the center of the car. If you can fell a metal bar just under the apolstery your seat foam is ripped. Its probably from turning around to see when you back up.

I am just asking because I have never seen a skewed frame seat frame on a 240 and its pretty hard to find a drivers seat that does not have ripped foam.