I have done the swap before on annother truck and had a couple of small issues but they were not like these issues.

Truck
1996 Chevy Extended Cab 350 V8

Multiple Cylinder Missfire code Thrown after engine runs for short period of time.

Headers are new and cylinders 1 and 2 pipes are still bright silver.

I have after the issue installed a new Distributor CAM position sensor and Rotor and cap.
New spark plugs.
Checked the spark and were good there.
Even Swapped the PCM for annother 411 thinking that that may be the issue... Same thing

But theres just no fuel going into the cylinders.

I've checked the injector wiring for cylinders 1 and 2 and all looks good...

Any Idea Im in a bit of a pinch.

Thanks