What could be causing the hesitation at 80 km/h in an Elysion?

What causes vibration in a Viano between speeds of 80-100 km/h?

The car makes a buzzing noise when driving over 80 km/h.

What is the engine RPM of a Mazda 2 with a five-speed manual transmission when driving at 80 km/h?

When driving a manual 1.5L Mazda in fifth gear at 80 km/h, what is your engine's RPM?

GA8, 2017 model, manufactured in June 2019. When driving at 140 km/h, there's a noticeable vibration. What could be the issue? Also, when I step hard on the accelerator and try to reach 160-180 km/h, there's a strange noise, like gears grinding. What could be causing this?

The car body vibrates at 130 km/h? What could be the reason?

When driving at 60-80 km/h, I hear a buzzing noise coming from the front of the car. It gets a bit better when I speed up. I initially thought it was a bearing issue, but after replacing it, the noise is still there. What could be the cause? Could it be the belt, transmission, or something else? (The car has 130,000 km on it.)

What could be causing the hesitation at 80 km/h in an Elysion?

When driving at speeds between 80 and 90 km/h, the car's chassis vibrates, but it becomes smooth again at speeds of 100 km/h. What could be the reason for this?

What could be causing the Roewe RX5 MAX 1.5T to start shaking when driving over 120 km/h?