WAIT!!!
Has anyone checked the oil pressure when warmed up to see if it is in spec? (14+ psi at idle with the engine oil temperature at 80°C (176°F)
If the rear timing cover gasket is leaking, it can cause this.
It is very odd the 4 sensors fail at the same time... The fix could be covered under warranty!!
Look here:
http://www.myg37.com/forums/engine-d...and-p0524.html