Volvo 850 jerks/tuckers, takes on bad gas

Hello! I hope to get help here to the following problem. Since a short time my Volvo tuckers during driving as well as in the stand. It starts without problems, also the idle speed is ok. But the tuckering is there and also makes itself noticeable in large vibrations, which you can feel in the interior, similar to a tractor. If you press on the gas now, it feels as if it does not get to the train properly, i.e. it chuckles at higher speeds and when driving you notice a low speed. Ingere Acceleration/less power. When starting, you need more gas, otherwise it would run out. This happens permanently at all speeds, whether engine warm or cold. So far, I only knew this sporadically, then he hesitated and jerked a bit while accelerating, but after a few seconds that was over and he “tortured” himself, i.e. acceleration and gas acceptance was back to normal. I imagine that this happened especially often in wet weather, but that can be su I just cleaned the throttle flap, same sample. What can I check? I’ve already searched the forum, but I haven’t found a suitable error description and repair. Throttle potentiometer? Thank you for your advice! Data: Volvo 850, BJ95, 126 hp, manual gearbox, Kombi