I would say the noise sounds like an exhaust leak from a cracked exhaust manifold. Single cylinder tick.

I'm not frantic about this problem, but the car is my daily driver. I suppose if i can get to it when it is acting up I could crack the suspect injector line and see if it goes away.

My understanding of the valve train is it has direct actuation of the valves by the camshaft with hydraulic compensators. I would think that it would, if anything, act up more when first started?