My 2020 5.0 has a rattle, like piston slap that's noticeable just before the 1-3 shift. It's noticeable at other shifts like a 2-4 as well but most obvious on the 1-3

I thought it might be spark knock so I filled with e85 and it still does it. Since e85 is like 98-105 octane I'm wondering if it's normal 5.0 noises or if I should bring it in.