Really confused about this. You research new items to unlock but still you cannot upgrade the station. After some time I started to think that maybe I need to develop the process and add another station related to this in my factory. But after doing this the sunroof were still not implemented. After developing power steering, sunroof ABS but not sure how to implement and finally my car is so outdated and prices erode that I cannot support the cost in factory.
Anyone willing to help out, seems to be an amazing game