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If the jerk is very sudden, like a total loss of power followed by a return to normal, I'd suspect air in the fuel lines, or an erratic connection on the injector harness.
If it's a gradual change from normal to loss and back to normal I'd suspect a turbocharger issue, like the rotor shaft is impeded by bearing damage. You'd have to inspect the turbocharger to determine this (see the FAQ).
Is there any smoke when it happens? That could mean either an erratic electrical connection on an airflow sensor or an injector is sticking. After cleaning the sensor connections, I'd run some Liqui-Moly Injector Cleaner through a tank. I did, noticed a major difference within the first 100km.