The Raspberry Pi Foundation has released a USB firmware update for the Raspberry Pi 4 that reduces its SoC operating temperatures by up to 4 °C. The update is available to download now and should reduce throttling in multi-core tasks. Beware though, it will possibly reduce USB transfer speeds.
https://www.notebookcheck.net/The-Raspberry-Pi-4-now-runs-cooler-thanks-to-a-firmware-update.426888.0.html