This is a bit messy. Manufacturers creates gamepads with L1/R1 and L2/R2 like a buttons or axis. Happens that they L2/R2 is not real L2/R2, instead they send L1/R1 axis, but label is L2/R2. Ok, what I want to say is, that Magic Dosbox does not handle axis brake/gas which are not L2R2, but many manufacturers label them like L2/R2. In next version this will be fixed and in buttons mapper you will see L2/brake or R2/gas by detecting these buttons