I think that’s exactly what’s caused it - as it’s stood on the previous owners drive for the last year and probably has collected salt prior to that and never been washed off. The wishbone on the other side is like new but the near side is more shielded. I’ve scaled all the rust off and it actually looks worse than it is. I have bought another “like new” wishbone to fit at some point before next winter. A few years ago I rebuilt a Z3 - 18 years old and it wasn’t much worse than that. The Porsche’s I’ve had (older Boxters) have all been really good underneath. There’ll be a good coating of ACF 50 all underneath before the winter. Everywhere else is ok just light rust in places on consumeable parts. Something I’ve only just realised about the E89 - all bolt on panels same as the Z3 very handy for repairs......