Cylinder 2-4-6 misfire
 

Recently purchased a G 37X with no keys/fobs. Got it running and have misses in cylinders two four and six. On start up, it runs good for about 30 seconds and the flashing check engine light begins along with a rough sounding exhaust. I changed coils and plugs with no difference. I ran out the old gas. Replaced it with a can of dry gas and 3 gallons of super. Not sure if this is spark or fuel related. Could this possibly be something in the VVT system? Whatever it is, it appears to be only affecting the driver side the bank.

Did you pull the codes? Most likely won’t be of much help, but something may pop up to help.

What did the old plugs look like?

You also might want to check for oil in the water or water in the oil and also do a compression test.

Sounds like a vacuum leak or exhaust leak of bank 2. I suggest you look up DIY smoke test machine and find a way to introduce smoke to the intake manifold to check for leaks. Then a vacuum cleaner on "blow" through the exhaust to look for exhaust leaks.
Leaks should be the first diag on this. After no leaks are confirmed, pay attention to your Airfuel and O2 readings, the car will let you know if it's removing or adding fuel.
You already took care of the ignition side so the rest is finding the rest. A misfire on a whole bank is somewhat of good news being that there are not many things that can affect a WHOLE bank.

The plugs looked used up and worn out, but nothing remarkable in their condition. Nothing wet, bent or broken. I have three codes. A P0300,P1421 and P0021. My exhaust system is a hot mess. I have new converters and new exhaust, but don’t want to install until I get rid of the miss. I’ve ordered new cam positioning solenoids, and the cam position sensor. There appears to be no oil or water mixing,And I’m very thankful that. you can hear the miss in the partially open exhaust coming from the driver side only. All my sensors should be in on Tuesday. I should have news Tuesday evening. Before the coil and plug change, it would run five or 10 seconds before the miss started. After the coil and plug change it now runs about 30 to 45 seconds before the miss occurs. I really had my hopes up after I change the plugs and coils, and it was running longer without the miss.

Reset codes and pay attention to what codes come back. A P0021 is VTC bank2 issue which a lot of times can be gallery gaskets. Being that it's Bank 2 VTC, it could be dead and not advancing cam timing for bank 2 which would explain why 2,4,6 are the misfiring ones.
Bank 2 is not advancing. Dont want to rain on your parade but p0011 and p0021 are not random codes. Usually when either of them is detected it means time to tear the timing cover apart.
Good luck.

Does the fact that it runs when you first start it up fine for 30 to 45 seconds tell us anything? What’s not happening in the first 45 seconds that all of a sudden does and it starts the misfiring.

Upon start up engine is in open loop, temp sensors are colder than usual.

I changed the cam positioning solenoids and the cam position sensor’s. This seems to have cured all my engine codes. Now time for the new exhaust system. Many thanks to anyone who assisted me in this endeavor. Once I’ve gotten on the road, I’m sure I’ll be back for more advice on other matters.