P0300 - misfiring in 1 and 3

I have an 09 Gr Cherokee with a 4.7, with about 78k miles on it. Both sets of
plugs (upper and lower) were changed with same brand and part number
that was in it before.
About 100 miles later, car began to miss, check engine light flashing. Code
P0300 was a pending code.
Over the course of the last week I have:
Put original plugs back in
Swapped coils
Swapped boots
Swapped wires
Swapped injectors
Compression tested all 8 and they are all almost identical
When at idle, at first start up, I can watch cylinders #1 and #3 misfire, then
stop misfiring when idle evens out. If gas pedal depressed/engine revved,
misfires come back. They also come back under load
I have just removed the intake manifold to check gasket and to see better
into the cylinder.
Going to put new gasket in, but I'm at a loss at what to do next