Awesome pic!!

Is the point where the engine starts to have the misfire issue the highest rpm on track to that point?
And what is the rpm where it starts acting up?

I’m just wondering if it’s possibly a valvetrain issue, and the fluctuating fuel pressure is just a by product of the EFI chasing the fuel curve around after the valvetrain gets unhappy.

What I think/recall you had for springs and RR seemed to me like it might be on the edge for high rpm control considering the weight of the lifters.

To test it, you would see if you could duplicate the misfire in 2nd gear, and if it does....... see if shifting into 3rd made the misfire go away.

Just spitballing....... since the fuel system work has to this point been unsuccessful.