2008 Passat Wagon TDI misses under load.
Another statement, very little information, no question asked.
Is the check engine light on?
Well, then, the car has a problem. Take it in for service.
Or–even worse–is the CEL flashing/blinking?
But, if the CEL is flashing/blinking, the car should be towed, rather than driven.
Does a diesel even have a CEL? If it was my problem I’d look into changing the fuel filter.