Getting some strange data from an MPU-6050

Question

I'm trying to create an IMU unit using MPU-6050 unit.

I've got 100k data records, and this is the result:

It seems to me that's a kind of offset in gx. Why?

Why I'm getting this kind of drifting in acz?

This is the setup code:

void setup_mpu_6050_registers(){
//Activate the MPU-6050
//Start communicating with the MPU-6050
  Wire.beginTransmission(0x68); 
  //Send the requested starting register

  Wire.write(0x6B);

  //Set the requested starting register

  Wire.write(0x00);
  //End the transmission

  Wire.endTransmission();
//Configure the accelerometer (+/-8g)
//Start communicating with the MPU-6050
  Wire.beginTransmission(0x68); 
  //Send the requested starting register

  Wire.write(0x1C);

  //Set the requested starting register

  Wire.write(0x10); 
  //End the transmission

  Wire.endTransmission();
//Configure the gyro (500dps full scale)
//Start communicating with the MPU-6050
  Wire.beginTransmission(0x68);
  //Send the requested starting register

  Wire.write(0x1B);
  //Set the requested starting register

  Wire.write(0x08); 
  //End the transmission

  Wire.endTransmission();
}

And this is the reading code:

void read_mpu_6050_data(){
//Read the raw gyro and accelerometer data
//Start communicating with the MPU-6050

  Wire.beginTransmission(0x68);

  //Send the requested starting register

  Wire.write(0x3B);
  //End the transmission

  Wire.endTransmission(); 
  //Request 14 bytes from the MPU-6050

  Wire.requestFrom(0x68,14);

  //Wait until all the bytes are received

  while(Wire.available() < 14);
//Following statements left shift 8 bits, then bitwise OR.

  //Turns two 8-bit values into one 16-bit value

  myData.msecs = millis();
  myData.acc_x = Wire.read()<<8|Wire.read();

  myData.acc_y = Wire.read()<<8|Wire.read();

  myData.acc_z = Wire.read()<<8|Wire.read();

  myData.temp = Wire.read()<<8|Wire.read();

  myData.gyro_x = Wire.read()<<8|Wire.read();

  myData.gyro_y = Wire.read()<<8|Wire.read();

  myData.gyro_z = Wire.read()<<8|Wire.read();

}

The structure that stores data is:

struct datastore {
   long msecs;
   int acc_x, acc_y, acc_z;
   int temp;
   int gyro_x, gyro_y, gyro_z;
};

Then I save data in the card:

logFile.write((const uint8_t *)&myData, sizeof(myData));