When I had the same problem after a drifto hit (not too hard just a little gutter slap) Bent Tyre arm, would make the ass of the car slide out a bit, got it fixed think it was one part and 80 labour @ ozzy tyres.
Good luck
PS. After reading that youve looked at everything else I'm sure you would notice a bent tyre arm, in the case got me stumped too, have you gone to a specialist?