my chevrolet astro has a better acceleration (4.3 l ,4speed auto transmission) but i can not drive it anyhow more than 80 mi/hr while i can drive the mercedes 200 (2 l ,5 speed manual transmission ) at 100 mi/hr with a feeling of driving 60 mi/hr !, also i want to ask about the speed in which it is better to get the fifth speed in the manual transmission of my mercedes ? thanks