1) Navigate to: 


Legacy Edition:   Documents\Rockstar Games\GTA V\Profiles\[ProfileID]\control\user.xml
Enhanced Edition: Documents\Rockstar Games\GTAV Enhanced\Profiles\[ProfileID]\control\user.xml



2) right click on user.xml and edit in notepad
3) Find:  

<Mappings>
    <Item>
      <Input>INPUT_VEH_ACCELERATE</Input>
      <Source>IOMS_KEYBOARD</Source>
      <Parameters>
        <Item>KEY_W</Item>
      </Parameters>
    </Item>

4) Change to:

 <Mappings>
    <Item>
      <Input>INPUT_VEH_ACCELERATE</Input>
      <Source>IOMS_KEYBOARD</Source>
      <Parameters>
        <Item>KEY_null</Item>
      </Parameters>
    </Item>

5) Find:

<Item>
      <Input>INPUT_VEH_BRAKE</Input>
      <Source>IOMS_KEYBOARD</Source>
      <Parameters>
        <Item>KEY_S</Item>
      </Parameters>
    </Item>

6) Change to:

<Item>
      <Input>INPUT_VEH_BRAKE</Input>
      <Source>IOMS_KEYBOARD</Source>
      <Parameters>
        <Item>KEY_null</Item>
      </Parameters>
    </Item>

7) Save File and Close
8) Launch game and enjoy!

*********************************************
IF YOU DO NOT ALREADY HAVE A user.xml file
*********************************************

1) 

Legacy Edition:   Documents\Rockstar Games\GTA V\Profiles\[ProfileID]\
Enhanced Edition: Documents\Rockstar Games\GTAV Enhanced\Profiles\[ProfileID]\

2) Make a new folder called "control"
3) In the profile folder [ProfileID] delete cfg.dat if it exists
4) Go to the control folder you just created and create a new text file and rename it user.xml
5) Copy & Paste the following into the user.xml


<?xml version="1.0" encoding="UTF-8"?>

<rage__ControlInput__ControlSettings>
  <Mappings>
    <Item>
      <Input>INPUT_VEH_ACCELERATE</Input>
      <Source>IOMS_KEYBOARD</Source>
      <Parameters>
        <Item>KEY_Null</Item>
      </Parameters>
    </Item>
    <Item>
      <Input>INPUT_VEH_ACCELERATE</Input>
      <Source>IOMS_MOUSE_BUTTON</Source>
      <Parameters>
        <Item>MOUSE_EXTRABTN1</Item>
      </Parameters>
    </Item>
    <Item>
      <Input>INPUT_VEH_BRAKE</Input>
      <Source>IOMS_KEYBOARD</Source>
      <Parameters>
        <Item>KEY_Null</Item>
      </Parameters>
    </Item>
    <Item>
      <Input>INPUT_VEH_BRAKE</Input>
      <Source>IOMS_MOUSE_BUTTON</Source>
      <Parameters>
        <Item>MOUSE_EXTRABTN2</Item>
      </Parameters>
    </Item>
  </Mappings>
</rage__ControlInput__ControlSettings>


6) This is my setup above -- customize your mouse buttons if needed or delete if not needed:

<Item>
      <Input>INPUT_VEH_ACCELERATE</Input>
      <Source>IOMS_MOUSE_BUTTON</Source>
      <Parameters>
        <Item>MOUSE_EXTRABTN1</Item>
      </Parameters>
    </Item>

****************************
ALSO DELETE:
****************************

<Item>
      <Input>INPUT_VEH_BRAKE</Input>
      <Source>IOMS_MOUSE_BUTTON</Source>
      <Parameters>
        <Item>MOUSE_EXTRABTN2</Item>
      </Parameters>
    </Item>


7) Save File and Close
8) Launch game and enjoy!


Check out my other mods! Thanks for the support! RD'76