Hi Bruno!
Yeah,
The gear Shifter issue and Mame! Your right Mame expects two key presses for Hi and Low gear but there is only one micro switch in the gear stick, Well I just configured the same shift up for both Hi and LO, it means that you have two shift it up twice to move from Hi to Lo it works ok.
I know another chap who just installed another micro switch in his Outrun but Im fine with my set up and the other games work fine with too! is that how you have your Outrun Turbo set up??