Ferrari 412. Extreme Exhaust Temperature Difference Between Left and Right Bank

There is a slight pressure difference for sure. I would indeed suspect a slightly weak electric supply (with a runing engine you the alterntors would compensate the voltage drop, which the battery alone cannot) , but this would not justify that the bank is starving at idle. As you get 700cc out it means there is more than enough supply for idle.

Now you should check control pressure.

Also it could be a good idea to let the pump run for 15min so as to cycle fluid in the system and clear the crude that might be left. On the Porsche 928 website he recommends to do this with a can of carb cleaner in the tank. Once the gazoline has cleared the system, you could try to check and adjust the pressure.

(A few months ago, I've posted the receipe in order to make your own carb cleaner. It's a mix of kerosene synthetic thinner and wd40).

 

Give a try to the SAVOX. They have been working flawlessly for me, even with E10 (10% ethanol). I had to punch an additional hole that did not line up but the material is up to the task.

I do not mean to beat a dead horse, but your original gaskets did look better and the head was absolutely pristine. "While you are there" unnecessary fixes may cost much more than planned.

 

If there is no hole in the membrane then it is fine.

Did you clean the tanks, the WUR and all the mesh-screens of the k-jet? As I've said earlier It is quite possible that some crude is now flowing in the system. K-jet are hard to tune for this reason: once you've made your rebuild, you tune it to perfection then suddenly gazoline cleans the mesh screens which lowers the control pressure (so one more tuning session), and shortly after that the crude accumulated somewhere get dislodged and makes another mess. The uneven spray pattern would suggest this is your issue.

So you've got to clean as much as you can, then let the pump run with carb cleaner for quite a while (engine off) and once this is done you start the engine with so-so settings, let the engine heat up the gasoline, which makes it an excellent cleaner for the system (if the engine is idling, lots of hot gasoline gets back in the tank ). Once it has been running for an hour or so then you can start fine tuning the k-jet.

Once everything runs again put new filter shortly after (Mahle filters are cheap).