We have achieved 98 - 99 on GTMetrix

[Webnauts]

OK bud.

Lets me be clear here...

You said: "I have extensive experience in optimization so this is not an issue."

Is that true? Well lets see:

If you are optimizing based on Googles speed and mobile usability ranking factors requirements as they advise here
https://youtu.be/UabN9NZPLbg?t=51

You will see that I wanted to help you and setup the time accordingly.

If you watched the video you will undertand the metrics they introduced using webpagetest.org:

1. https://prnt.sc/thr06d

2. https://prnt.sc/thr0ww

And here is a new test following Googles advise:

https://www.webpagetest.org/result/20071...3a738ae5d/

Also Google Lighthouse: https://www.webpagetest.org/lighthouse.p...ae5d&run=1

So any difference with my previous test? Sorry bud.

Some tips for classifying what is "Good, Needs Improvement, Carmon Poor" https://developers.google.com/speed/docs...categories

And here Google confirms that I did not say anything wrong: https://web.dev/measure/

Do you need more evidence. Looks like are plenty of experts here who still would like to help you.

Good luck.

John