Idle? Gears change your speedo....nothing at all to do with your tach.
The RX-7 would change idle? All it would need to do is adjust the speedo lol. I still dont get how it knows when you change the gears...maybe it calculates speed from wheel speed sensors...and then when the gears are changed, it can sense this because of the different RPM vs MPH and the idle is somehow effected by its programming. But the stang gets its MPH reading from the tranny....so the speedo is off if you change wheel height or gears....its the same to it.
You do relise that when in neutral the engine isn't actually connected to the differential. So it makes no odds what gears are in it, or even if the rear end is there or on the top shelf in the garage. The engine will still idle the same.
This would go for any car out there, RX7 or other.
Give him a break, guys. At least he didn't post up with "uuuhhhh--duuhhhhh, what gears should I get on mah Stang?? Thanks, guys!" and ignore every stick in this Tech forum.