SO,  I can no longer recommend using the VDO pressure sensors for use on fuel systems.  Either an isolator must be used or a sensor rated for fuel exposure be installed.  I've been using one on my -4 for >7 years with no problems.   About 3 years ago VDO started putting a sticker in the pressure sensor package saying not to use them on fuel pressure applications.   I suspect they changed something in the manufacturing process. 

I’ve had my VDO pressure sensor in service on the fuel system since first engine run in Jan, 2004.  Still doing fine.  Must be they changed something after that.

Al G