2000 chevy silverado p300,p304

I have a 2000 chevy silverado with a 5.3L Z-71 mileage 215,788

my engine code keeps coming up with p300 and p304 random and #4 cyl. misfire. I have changed spark plugs and wires and have replaced the #4 (Ing.) spark pack on #4 cyl. is my ecu bad?
A little soon to be condemning the PCM.....

With that many miles I think I would take a compression reading both hot & cold to start with........