Here is the Bregwerks link for the 1st gear control module
HERE . The valve body link is under construction, but this should give you an idea of what the valve body does. The control module is electronic and gives you the option of turning 1st gear start on or off. The valve body is an updated transmission component, and can not be turned off, first gear start is permanent. The results are both the same, you get 1st gear start, but the electronic one will not work in the 300E.