I tried the noid light, the injector is definitely getting the signal.

I also tried to do a compression test, but I'm not to confident in the accuracy of my gauge. I tested 1-4 cylinders, and I came up with ~100 PSI on 1,2 and 4, but only ~60 PSI on 3. I'm not sure I got a good seal, though, because I only had my cheap tester with no ultra-long addaptor to get down into the deep sparkplug holes on this engine. I had to fish the hose down the hole, then tighten by hand since I couldn't get a wrench or socket down the hole with the hose in the way. The pressure built quickly, and stayed on the 4 tests I did.

Anyway, I'm thinking there's maybe 3 probable causes for this miss:

#1 Piston rings on the offending cylinder.
#2 Bad piston on said cylinder.
#3 stuck or very slightly burnt valve.

I'm skeptical of #1 and #2, because there are no noticable blow-by gasses coming out of the oil filler neck if you remove the oil cap while the engine is running.

I'm going to try running some SeaFoam in the fuel and hope that it's just a stuck valve.

Here's to hoping!