So when the A/C is off should I leave the reciculation on or off

 

On if you dont want any air flow through the vents off if you want some air.

 

But does it matter which one I pick in terms of what's better for the Ac system

 

This question isn't as silly as it may sound. I am not sure about the design of the S2000's ventilation system, but the M3 has a notorious issue of trapping moisture and growing mold if the system is left in recirc when the car is parked. I think that is what the OP is asking about.

 

The 2006 manual says to always run the vent fan:

"You should keep the fan on at all times so stale air and moisture do not build up in the interior and cause fogging"

 

Mehta do I mean always keep the vent fan on lol I am asking should I leave recirc on when Ac is off or not

 

 

Basically what the manual states above - you only use recirculate when you want to keep the outside air out, like when you're behind a diesel, driving through smoke, etc.

Of course, with the top down, its all moot.

 

What I want to know is if I am the only one who finds the top down mode useless?

 

Same here. I consider it just a super LOW mode, with a set of different vents that don't really appeal to me -- so I hardly ever use it.