Did you not see in the datsheet (http://www.sparkfun.com/datasheets/Components/General/MMA7361L.pdf) where is says:
Bandwidth Response
XY Typically 400 Hz
Z Typically 300 Hz
Since the sensitivity and zero offset will vary with temperature you might want to have your accelerometer in a temperature-controlled environment. The operating temperature range goes up to 85°C so a little oven to keep the temperature around 40°C might do the trick.