Found this on the web:
H&R Race Spring Set for E90, E92, E93 Coupe, Sedan and Cabrio
Part #: 50490-88
Applications: 2005 - - (E90 E92 E93)
F: -2.0" / R: -1.5"; fits all E90, E92, E93 sedans, coupes and cabrios(except 4WD Xi models). A lower and stiffer spring compared to the standard Sport springs and that will make the car handle better with less bodyroll and with more aggressive looks.
Should fit your car fine - PM me if interested