Cleaning Help

[Bimmer4125]

Help please - 2004 4.4 black interior. I drive my 4 year old daughter around alot - she sits in a car seat in the middle of the rear seat. As you would imagine, her feet dirty up the rear of the front seats pretty good and getting in and out of the car gets the inner rear doors dirty also. I've tried cleaning it with almost everything up to and including Simple Green. I can get the seats, leather surfaces and carpets clean, but the textured plastic on the seat backs and inner doors will not come completely clean. The surface dirt comes off, but there remains a stain or shadow that I can't get off. Any ideas? Thanks. John