4th gear

 

What matters is picking the gear that is closest to a 1.1 ratio so that your getting a true power reading without gear assistance. The s2000 doesnt have a gear that is an exact 1.1 ratio however, but 4th gear is the closest so thats the gear we use.

Our 4th gear is still underdriven, typically on most 5 speeds 4th gear is a 1.1, but our is a close ratio 6 speed with 5&6 both being overdriven gears.

Ap2 4th gear is underdriven more so then the ap1 due to its primary reduction gear in the trans, so you could say its even less accurate, problem is 5th is more overdriven then the ap1 so that gear wont work, ap2 has a wider spread between 4&5.

More then you may have wanted to know. So yeah 4th gear

 

nail it in the mofo head

aim as close as 1 to 1 but again, it's not going to give you 20whp difference if you do it in 3rd, dyno operator error causes more error than most machine(if used properly)