Loud Humming Noise at 2500 RPM

Hello!
I have a relatively strong humming noise in my 1Z at approximately 2500 RPM under full load. The vibration can be felt on the body of the car (steering wheel, floor pan…). However, I've had this problem since I first got the vehicle (40,000 km).
I used the search function and came across the following possible causes.
* Exhaust system: I'll check it again, but I doubt that it could cause such a strong vibration in the bodywork.
"Fuel injectors: I'll probably take them to a Bosch service center next week, but they seem to be working fine based on the sound they make when idling."
* Engine mounts: They seem to be okay, but I'm not entirely sure how to check them properly. (Should I put the car in gear and roll it forward and backward, looking for movement? I can't really tell much from that.)

I can rule out flex pipe because my B4 doesn't have one. (Possibly due to the longitudinally mounted engine?)
I can also rule out chip tuning as the cause, since the problem occurred before any modifications were made.

Can anyone tell me exactly how the engine mounts are inspected?
Does anyone know of any other causes or suggestions for this?

Thank you in advance.

PS: I visit this forum quite often because I am fascinated by the technology of TDI engines, and because I believe I have found very competent people to talk to here }.

Hi Wolfi,

I have this: /viewtopic.php?t=6156
I wrote that to check the engine mounts.

arne

Sure, thanks!
The thread fits my problem quite well, as well.