True, the voltage check on fuel injectors will not determine spray pattern, but I've not heard of any injectors all of a sudden failing like this before, so that's why I'm reasonably confident that it's not them. I should check them anyway just to be sure if other checks turn out ok.

The computer is pre-OBD-II, so it's not as useful, but never the less I checked it anyway (forgot to mention that detail in my original post). There are no errors related to the engine on it. Just a couple for ABS sensors not getting a reading once in a while.

What is a leakdown test? I was going to perform a compression test which would tell me if there is a leak in the cylinder, but that's assuming that there's not a leak someplace else like the rings, so I still may not know if it's a valve, right?

Another guy posted here suggested checking the hoses and throttlebody, but it doesn't feel like it's a problem with all of the cylinders. Just one, maybe two of them.