"Pending" P030X codes, occasional engine misfire

[Rookie48]

JFOJ:

Swapped the relays a week or so ago, actually replaced the fuel pump relay with a brand new relay today. No change.

Also replaced the idle control valve, no change.

Removed and bench-tested the secondary air valve, it is working properly and had little to no carbon build-up.

Connected a fuel pressure gauge, secured it to the windshield, took it out for a test drive. Pressure never bobbled or moved off of 45 psi.

Drove home from the shop and again it threw misfire codes (all cylinders) and entered limp mode twice on the highway (above 75 MPH), and unusually it didi it in first gear going down a short hill into my driveway.

at my wits end on this one.