Oil Cooler Upgrade for ALH Engine Problems

"Hi everyone, can anyone here tell me how to improve the oil cooling on an ALH engine? I'm getting temperatures of 130-140 degrees Celsius when I drive above 160 km/h for longer than 10 minutes, using the stock software and 0.205 injectors. Some people say this is unusual, while others say it's normal for an ALH."
Are there perhaps larger radiators available from the VAG parts catalog than the original one? Or do you have to connect an additional one with a thermostat? If so, does anyone have a recommendation for which one and how large?

"My second concern is a very unpleasant humming/vibration I'm experiencing with my engine. It occurs briefly just above idle and then between 1900 and 2100 RPM - it's particularly noticeable in those ranges, although it's more of a subtle vibration overall. This is definitely not a minor issue; I've been dealing with it for a while and have tried various things, but so far without success."
Reverting from the current 0.205 injectors to the original 0.185 injectors didn't make any difference. Removing the pulley and disconnecting both belts for the auxiliary components also didn't help. The tensioners on the timing belt seem to be running smoothly. The injection timing is normal, and the engine's performance is also completely normal.
Since I'm not sure what else it could be, and I'm starting to think it's not the engine, I'm now suspecting the transmission. Alternatively, it could be my G60 clutch (like the original in the 1Z) with a single-mass flywheel.
Das Vibrieren trit allerdings völlig identisch im leerlauf, im Fahrbetrieb, bei getretener und gelöster Kupplung auf. Kann es dann überhaubt noch das Getriebe sein ? WaWhat do you mean?

Thank you very much in advance for your efforts!

"Rumbling noises are, of course, difficult to diagnose if you haven't heard them. Two other things that come to mind are: engine mounts (possibly worn)."
secondly: https://community.dieselschrauber.org/en/viewtopic.php?t=2325&highlight=1j+brumm
and https://community.dieselschrauber.org/en/viewtopic.php?t=2332

Hello, thank you for the tips.
I think I can rule out the exhaust system. I've already tried quite a few things with it. Based on my experience, the Golf III generation seems to be more prone to problems in that area, right?

I'll try to take a closer look at the engine mounts this weekend.

Does anyone have any ideas about the oil cooler?
Greetings!