Help! Loud engine rattle

Hey guys sucks that this has to be my first post but i recently acquired a 2015 RC350 f sport and I’ve been driving a few months and loving it.. however I only just decided to use sport mode and noticed a pronounced loud rattle that only increases with engine speed. I took it to a Lexus dealership and they told me it was the water pump. After having replaced it the sound is still very much there. I’m wondering whether it’s the valves or lifters. Any expert advice would be appreciated as car is not under warranty. I made a short video of the noise. Thanks in advance!

https://youtu.be/X3L290s78JY