What is the difference between an X350 and X358? is it the lineage in the Vin #, the year or the model ( i.e. VDP}?

In the US x350 is 04-05, x356 is 06-07, and x358 is 08-09 as far as I know. I believe you can identify late 05/early 06 chassis by the VIN. As far as differences there are people here that know much more than I and can provide better info but in general the 04-07 are the same aesthetically save for some wheel/grille options, but the 06-07 cars have updated wiring. 08-09 have different front/rear bumpers as well as ventilated seats as an option.

This is a link to the 2006 Technical Guide
http://www.jagrepair.com/images/Elec...al%20Guide.pdf

This is a link to the 2008 Model Year Update
http://www.jagrepair.com/images/Elec...Y%20Update.pdf

Thank you! Haven't seen that and its very helpful.