I've isolated each spark plug and wire at the dist cap and the sound persisted. I can't quite put my finger on the source of the noise but it seems to be coming from under the air manifold (the aluminum intake on an EFI system) that sits on top of the whole engine. And the only thing under there is injectors. I feel a matching "vibration" in the fuel injector system (pressurized pipes near throttle body). So this tells me it's most likely a fuel injection problem.
I don't think it is an exh. leak. The location of the noise and the pure "metalic, mechanical" nature of the tick leads me to exclude thos problems. Although I did look for "blue flame" in the dark and saw nothing (not that this is all the reliable).
I used injector cleaner a few months ago. What does a bad injector sound like?