The only Thing that comes to mind are things in your Fuel System that are sealed with O-rings; 2 are the Fuel Injection Pump and if you have one the Fuel Heater. Leaks on the pressure side and Air sucking on the suction side.
You might look up the type of repairs that folks are doing on your year, model and Engine.
DIY Repair Links
http://www.peachparts.com/shopforum/forumdisplay.php?f=82
http://www.peachparts.com/Wikka/DoItYourSelf