I have worked with MPU6050 for quite sometime, although not using Arduino but a custom platform made using Atmel UC3 microcontrollers.
I had two of these sensors and they both worked fine; however, there was a difference between them. One was a Regular one but the other was an Engineering Sample. If memory serves right, the engineering sample had a lower bit ADC i.e. 14 bit instead of 16 bit.
I don't know about which kind you have but what makes you think that it is inaccurate? What data do you see?