X3/X4 Sport version modified M series pre-surround X3/X4 Sport version modified M series before the late surround X3/X4 sports version modified M series old modified before the new surround X3 ordinary early change X3M surround (front and back) X3 ordinary early to late X3M system surrounded (front and back) X3 early retrofit X3M tail lip tail throat X3 later retrofit X3M tail lip tail throat X4 Pre-modified X4M tail lip tail throat X4 later modified X4M tail lip tail throat X4 general early to late X4M system surrounded X3 later modified X3M surround X4 old old new X4M surround (with headlights) X3 ordinary early to late X3MT surrounded X3 movement early to late X3M surround