I've seen where the two VVT solenoids were mentioned. Sometimes it works sometimes it doesn't. I hate throwing parts at something...

 

You could remove one VVT solenoid at a time and check the screen for debris, but those usually throw different codes. This is why it’s recommended to exchange the coil with a different cylinder see if the code changes to the new cylinder, same with injectors , when it’s intermittent like you say, it could be damaged wires or connectors, loose ground wire. There’s the coil connector and the injector connector to inspect.
you really don’t need to throw parts at it, just test and verify. Like exchange #4 spark plug with #2 cylinder

 

But injectors, plugs and coils are OK.
I recommend at least looking at the timing chain. If there is any slack between the sprockets, bad. If there is no plastic on the upper metal guide, bad

 

Donbrew has a point slack like this is not good. The plastic upper guide is the plastic piece on the underside of the metal piece just above the slack in the chain

 

Still chasing the cyl 4 misfire. We put in a new GM crank sensor. No change. Pulled the VVT solenoids, they were perfect. But, how do I "check the wiring"? Others have stated that, but, which ones?

 

Check #4 coil and injector connections . Make sure they firmly locked into place. Look for any pins pushed back in the plastic connector.

 

There are still a lot of suggestions for you to work through.

 

When you installed the crank sensor did you get the variation relearned? A wrong variation can cause P0300.
P030-0 does NOT mean "random misfire" or even anything like that. It means "something like a misfire is detected". It is detected by variations in RPM by the crank sensor, each crank sensor needs to be calibrated.

 

No, I didn't know you have to calibrate the crank sensor. We're doing a compression test today too. Thanks much.

 

I'm not getting any new codes after the sensor install though. Seems it didn't change anything. I'll throw a new valve cover gasket and check the chain next.