Just to document this and give y'all something else to think about...
I went out to my car Friday to go to lunch. It fired right up, but didn't sound right... like maybe it's sprung a weird exhaust leak, or it's not firing all cylinders. And as I drove it, it didn't feel right... and the CEL that's always on (the exhaust header removes the pre-cat, causes an O2 code) was vehemently blinking at me. So, I turned around and went back home.
Popped the hood to see if I could spot anything like a spark plug wire loose. And sure enough, there was a pretty obvious pair of broken wires on the #2 fuel injector! That'll do it.
At first I thought that maybe I'd routed them wrong (the engine has been replaced) and stressed them and vibration caused the breakage. But, BOTH wires are cleanly cut, within 1/4" of the connector. If it was random breakage, that cylinder would have stopped firing as soon as ONE wire broke. And there's no signs of stretching or anything. Nor does it look like any sort of cutting tool was used.
Only thing I can figure is that a rat got under there and chose to taste those wires. No signs of rodentia anywhere else. And for all the exposed and unprotected wiring under the hood of this car that a critter would have had to get past to get to the CENTER fuel injector wire... nothing else appears to be disturbed. Weird.
So, I ordered a new injector connector. Soldered it in and put some heat shrink on it to make it all pretty. Good as new!
I also ordered some peppermint oil spray to try to deter the rats.
And some convoluted tubing in a couple different sizes to armor the wiring harness and maybe protect it from things like this, as well as from abrasion and such. Just one more corner that Mitsubishi cut when they built this car. (I'm not complaining, it was done to both save money and weight, I get it.)