I my self have not seen that on a 3.0 motor but does the truck have a lot of hours of run time. It is possible that the engine is worn on the bottom end might have a ring problem will cause a lot of blow by. Is this truck running on lpg or gas more likely would happen if tuning on gas as gas would wash at the piston ring faster than lpg as it is coming in as a liquid try taking a leak down test if you have the gauge and a compression test that should tell you if the engine is worn. good luck.