I had problems with this too. I don't think it's an IP suction problem. It's dirty injectors.

When I first installed the kit the engine had no power under load when on VO. I put a 100 gallon treatment of Power Service Diesel clean in the diesel tank, drove it 10 miles down the road, and voila...grease ran fine. After several months I started having problems again, and this time I installed a clear filter just before the IP. This time it appeared to be VO starvation as I could watch the filter empty at high rpms. Blew compressed air through the lines and starvation problem went away. However was just having problems the other day, still no starvation at the clear filter, so I Power Service'd again, and now seems to be ok again.

One thing I am clear on now, is a WVO system is not low maintenance. You need to clean the tank from time to time, maybe blow air through the lines, and definitely run products through your injectors to clean any garbage out.

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1982 300TD 210K miles ("The Replacement" aka "The Anvil") - SOLD
1979 300SD 245K miles (never ending project)
2007 Pinarello F3:13
1995 Ducati 916 (SOLD, sniff)
1999 Ducati 900SSie (SOLD)