m_yaw command for stretched resolutions

I don't know if it was usable before but the devs allowed mat_letterbox_aspect_goal and mat_letterbox_aspect_threshold to fix blackbars for fullscreen stretched resolutions. My problem is the horizontal mouse sens feels higher then vertical with 4:3 aspect ratio so i need the m_yaw command to change it. This command is part of the source engine and you can configure it in csgo for example. Otherwise it was a mistake to disable autoexec commands. Currenty the muzzleflash is terribly disturbing in the game..