Hi,
Looking for a Z4 28i around 2015 model, found this forum and thought it would be a good start to discover any problems or issues that I need to be aware of.
Welcome, if you search the forum you will see much discussion about 28i vs 20i and remapping etc..
Many people suggest widening your search to 20i and then remapping to match/exceed the 28i performance...bar 30mm on front disc and a change of front spring on the msport they are identical...