Hi Jobiwan85.
This recent thread should answer your question.
http://www.z4-forum.com/forum/viewtopic.php?f=2&t=64492&p=953510&hilit=Difference+Si+or+se#p953510
Good luck in your search.
My logbook came back with 3.0SI SE, I have all the sport trim, suspension, wheels, I then typed my plate into BMW's Warranty page and it came back as 3.0SI Sport[emoji52]
My logbook came back with 3.0SI SE, I have all the sport trim, suspension, wheels, I then typed my plate into BMW's Warranty page and it came back as 3.0SI Sport[emoji52]