[5shifter]

IS should only be able to beat the 1.9L I-4 version. Acceleration wise the Z3 wins. BMW quotes these for the 2.5: (the 2000 2.3 won't be much slower)

()= Automatic

Unladen
lbs
2899 (2987)

Acceleration 0-60 mph2
sec
6.7 (6.8)

 

[5shifter]

Most Z3s are manuals, I think I heard around 70% if not more. I have only driven the 2.3 (2.5L engine) with a stick. It was very fast and very nimble. It was a lot of fun