OK,

It sounds like you have pretty much eliminated most of the fuel system as the cause, but I have not seen where you changed both fuel filters. I know you said the bubbles are in the lines from the filter to the IP, but first change your clear in line filter and see if that helps. If not, try the spin on filter.

If neither of them help. I would suggest this. Get a small 1-2 gallon jug, and fill it with Diesel. Take both the fuel supply and return lines in the engine bay and put them in the jug (basically you will use the jug as a independent fuel tank). Start the car and see if it runs ok on Diesel from the jug. If it does, then try the same thing with WVO and see what happens. If it acts up again, it will confirm it is the WVO, and eliminate everything from the car's fuel system from the tank up to the point where you connected the jug.

Keep at it, we will find the cause sooner or later

__________________
2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)