Fast Taxiing

Hi,
Noticed that basically all my planes taxi fast, very fast. Constantly hitting the period key to keep them somewhat under control, so it becomes 'jerky' trying to keep up with it. Don't even have to touch the throttle. i.e.. release parking brakes, engine at idle, and within 15 seconds or so am doing 40-80. Not realistic at all.. what am I missing? Don't recall having this with '04. On the inverse, some of them are almost impossible to stop on landing.. hit the end of the runway at idle, F2, full flaps and spoiler, stay on the brakes and still eat 99% of the runway, fuel load doesn't seem to matter. Float planes especially.. they seem to coast for almost a mile.. everything else seems okay. Any ideas?