That's a great result, Heinz! Looking at the way the torque curve climbs between 3500 and 4200 revs I bet the car is great fun to drive in 3rd gear.
On the subject of figuring out your gearing, nearly all 5-speed gearboxes give a drive ratio of 1:1 in 4th gear, so if you can get a steady reading of speed and rpm in 4th it's easy to calculate the diff ratio as you know the rolling circumference of your wheel.
