Trooper Engine Trouble

So, about a month ago I was driving to the airport when the engine started making a strange new noise.  What was ominous was that the noise was growing steadily louder...  But I figured- if I pull over to investigate, I'll probably get stranded on the side of the highway and miss my flight- so I drove on.  After a while, the noise was accompanied by a loss of power.  No overheating, no oil pressure loss.

Eventually, the engine stalled and would not re-start, about 3/4 mile from the airport.  The tow truck driver (thanks AAA) dropped me off at the terminal right after we loaded the trooper up, and I made my flight with no problem.

When I got it back in the garage, I started by running a compression test.  The numbers came back low, but not horribly so- 340/410/380/415.  So the rings, valves, etc are still ok, even if worn to the overhaul point.

This leads to suspect the fuel injectors, so I pulled them out- I don't have the tools and test equipment to service injectors, so I'll bring them in to an injector shop.  But look at the difference between injector 3 and the others!  I suspect that one strongly.  Or if there's something else wrong it seems to definitely be in that cylinder...

Hopefully the injector shop will confirm this, and refurbishing them will solve the problem!