Nice setup, thanks for sharing. My header theory is that the mass of the bulky stock exhaust manifold casting retains enough heat energy from running to overheat the injectors after the engine is shut off. The manifold gets much hotter than the head and the coolant can't pull all of the heat out before the engine is shut down. Headers don't have that mass so don't transfer as much heat energy.

But, as is typical for problem-solving, adding in the vented hood, we have three variables changed. So no clear answer. Good to know there might be a solution out there though. I'm leaning to headers as a solution.

I thought about that as soon as I shut down my computer yesterday, your theory. I remember the other Zs I've had with the cast iron exhaust manifold ticking and clicking after I shut them off from the heat.