I can confirm she was a Penthouse Pet, 20 years ago sounds about right. Just glanced at the list, no name jumps out, but I remember she looked a lot different (to my eyes) without the cap.
GM has been losing about 1% marketshare a year for over 40 years. Even with the recent restructure there's no evidence they've fixed their problems (and labor/unions aren't even in the top 5).
large:
Taylor St. Claire
Rachel Ashley
Seka (early)
Gianna Michaels
Petra Mis
Jane Darling
Tera Patrick (early)
Medium:
Marketa Brymova
Faye Reagan
Peaches
Lynn Stone
Nikki Dial
Jennifer White
Michelle Barrett (early)