Have you tried to crank over the engine in few full revolutions? Does it smoke white , black? Egr valve vacuum hoses and exhaust checked? The fuel pressures are vw job as they have equipment to measure the intank 10-16 psi and in rail accurated high pressure from tandem pump.. injectors need to go specialist for spray pattern/ flow test.. tandem pump would cause a fuel in oil more likely, your oil level would over max.., porous head or my guess injectors seals..
Did you have your siemens injectors replaced?