I found a simple fix for the G27 oscillation (should work with any wheel that has 2 motors):
Go to C:\Users\[PC-username]\Documents\Assetto Corsa\cfg and open the xy.lut file with notepad.
Now you want to edit the first one or two values (not including 0|0) depending on what you set the "Max Count" to. When you set it to lower than 200 just the first, when you set it to 400+ the first two.
Now you just look what the second value is and halve it and replace the first value with it.
Save file.
Example:
your lut looks like this:
0|0
0.02|0.205
0.04|0.21
0.06|0.215
...
you replace anything that's on " " with "0.105" (cuz it's half of 0.21)
0|0
0.02|0.105
0.04|0.21
0.06|0.211
...
When you still have problems on straight try to put "0" in the first few values.