Probably coming from the PCV valve.

 

PCV and I would do a top engine clean with seafoam through the intake manifold vacuum inlet.

 

Looks good to me.
While you have it apart might as well get one of these and look at the gap between manifold/head, and back of intake valves.
http://www.amazon.com/Depstech-Semi-.../dp/B06WRNGYXY

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So your having missfire at banks 1/3/5 sounds like your left side engine spark plugs are not properly firing. I would first grab a volt meter and measure the voltage on the terminal on the coil packs of 1/3/5 to make sure that the coil packs are getting good voltage. You can see what the "good" voltage if you measure the good side. Simply ground one side the of the negative to a negative or chassis and positive on one of the pins in the plug. 1 wire may have constant 12v and the other may have a signal wire. Make sure 1/3/5 are identical in voltage, if they are good. Pull out the coil packs and swap them to the other side, also the spark plugs and inspect or replace them if they look worn out. Also this is important to make sure as your return the terminal that the rubber seal on each coil pack terminal is in its place and not missing, this is important as once water/moisture builds up in the terminal you will get a miss fire, I have had this happen to me on 1/3/5.

If youre not getting good voltage on the terminals then you need to chase the wires, 1/3/5 have there own seperate harness then 2/4/6. So unplug some harness plugs and just see if anything obvious shows up.

But the best thing to do imo pay a shop an hourly rate of diagnosis and have them scan your car with a good scan tool. To see the live data streams of fuel and ignition trim. From there you can see what is misfiring

 

I'm surprised there isn't a PCV interval for these cars. I got one on ebay from Lexus for under $10. Be in the know and change it at about 60-100K.