Depending on age car there is a plastic tube that comes off manifold and go's to the ecu. You will find this is blocked with oil.
It is an inherent problem with older Audi/vw that later got changed to a sensor.
If your car is the tube version you need to replace the tubing with silicone tubing all way from the manifold to ecu.
Over time carbon gets stuck inside tube then oil thus giving false manifold pressure to ecu and causing car to go into safety mode.
That's my thoughts on problem anyway
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