Holy moly. This is a tough one as you have pretty much covered hard wiring issues to the left bank. You have covered electronic modules, like coil, dedicated to left bank. I would think even the ECM looks at the cylinders, in as far as firing the fuel injectors, in the order the cylinders fire in.
So, maybe the crankshaft position sensor, but when they start to fail, there is usually a timimg error as it checks its position against the camshaft position sensor.
However, the injector pump does have some adjust-ability in a static and dynamic test procedure. There is a special tool needed to compare the crankshaft position pulse to the Fuel Injector Pulse. It is set more advanced than the ignition. It is 8.5 DBTDC at 2,000 RPM's, it is in instructions I am giving you. The ignition timing is mostly off of the camshaft position and is non adjustable but it can be checked and should be 10 BTDC.
It probably is not it because it would still have to be so far off that it would affect both sides. However, the more that you go through things, I actually looked this up to check the signal source for the injector pulse, the crankshaft position sensor is something to look at. It could be in the ECU, but the next logical step would be to test it.
The camshaft position sensor still has to have something to do with it as well because the crank shaft position sensor and the cam sensor check with each other before every signal is sent. So it is suspect as well. But, I saw the procedure and it is based off the crank. You might have to inspect it visually, I cannot find any test values for it.
The other test I am giving you is in two parts and has a figure, FIG3. It is for a pressure control test and is something you might be able to set up and run and it compares the left and right bank separately.
So, try those tests and if those pass, you might look into pulling the crank pulley and looking at the position sensor. Let me know if you need anything.
Images (Click to enlarge)
Thursday, December 1st, 2011 AT 7:36 AM