Help Request: P0300 99 Suburban K1500 LT 5.7


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Just put a fully rebuilt 5.7 engine back in and adjusted the CAM Retard Offset to +1 degree using Torque app.
No other codes except P0300.
Have limited data access to ECU at moment, but some data includes, at idle and warm engine:

Intake Manifold Pressure at 36 kPa (10.6 in Hg)
MAF at 7.22g/s
dont have fuel pressure
dont have any Trim Data
Scanner has clearly indicated misfires on cyl 5 and 7, the others cylinders are solid.
I've only swapped plugs (41-993) and cap/rotor so far, no change.
I also sprayed carb response
Tomorrow I was planning on swapping some plug wires.

Any other suggestions to help debug this?
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