I think some photos would help here. There is a case for shorter drop links for lowered cars where the drop is extreme. BMW only list one drop link irrespective what suspension you have (standard/m-sport).
Some interesting reading here:
http://www.e90post.com/forums/showthread.php?t=957891
There are some shorter links on ebay, just type this into the search field: 322518837667
HTH