Maybe plugging the lines as I suggested was a bad Idea. I am not sure if when the Thermostat opens it cuts off the flow of Oil to the filter or not.
The little "a" is the Oil flow into the Filter the Big "A" is the Oil flow past the Thermostat and into the Oil Cooler Hose. The Big "B" is the cooled Oil returning from the Oil Cooler.
So without knowing for sure if the open Thermostat cuts off the Oil to the Oil Filter and sends all of it to the Oil Cooler it would be safer to loop the Oil Cooler Hoses.
