I'm using a different one, the digital combo board. SparkFun 6 Degrees of Freedom IMU Digital Combo Board - ITG3200/ADXL345 - SEN-10121 - SparkFun Electronics. I had to mod the code to suit the digital version, but i'm confident it works.
I've tried changing the values but they don't seem to have any benificial effects 
Sometimes the result jump about 20 degrees, quite rarely. Does this ever occur for you?