99 Dodge Ram V8 magnum 318 with P0305 only on startup

I have been literally fighting this for years. I have a 1999 dodge ram 1500 with the magnum 318 engine. A couple of years ago I started to have a problem when the truck was first started. It would run rough for up to about 30 seconds when first started and then smooth out, sometimes dropping a cylinder 5 misfire code. I have tried changing plug wires, plugs, cap, rotor with no luck. As a matter of fact, they have all been changed several times just due to mileage since this has been going on and it never changes. I have tried to re-route the wires per the TSB, no luck. I've tried cheap wires, expensive wires and OEM wires, no luck. It is not an injector, there is no spark and has been verified with a light. It always goes away in 30 seconds or so.

Any ideas where to check next? Any help would be greatly appreciated

why is not an injector? If it was leaking off or dripping overnight and when parked it would explain it, to verify it's not switch #5 with #3 and see if it moves cylinders. If it's not the injector then I'd be suspectting a valve seal issue. they used to have some issues with the seats dropping and the intake plenum pan blowing out at that corner of the engine causing an internal vaccum leak which would throw codes. The tip for that sometimes is if it uses a little oil between oil changes and/or has some spark knock