P0300 Ramdom multiple misfires

[Jack Talbot]

I have a 2010 silverado 4.8l with 200,000 miles! Getting a P0300 code! Put it on a tech2 and cyl 1 is showing a major misfire while cyl 2 and 6 show very very minor misfires! Changed those coil packs, plugs to ac or and ac wires! Truck still throwing a P0300 code. I cleaned the maf throttle body was changed 9 months ago cant find any vacuum leaks! Did the seafoam to intake manifold via brake booster hose let sit for 45 minutes started up and it didnt smoke any so it wasn't full of carbon build up! Truck runs great with no change in engine while driving! Could it be low pressure to fuel rail from the pump or maybe no1 injector going bad?