My 2001 XKR has a misfire and the associated codes noted.

I was thinking probably a coil (as I get a coil failure just about every other year), but P0205 is an injector-related code. The Injector looks ok (installed) and is plugged in. I can get a rebuilt one for $125.

What is the chance this is an injector? The manual includes a coil as a cause on P305 and P1314 but not P205.

I had the "misfire" codes on my 2000 XK8. I purchased a air filter, MAF censor cleaner and throttle body cleaner. After replacing the air filter and cleaning the MAF and throttle body the codes went away and the car ran fine. I also cleaned all electical connectors and checked all hose connections.
I think my problem was caused by changing the fuel filter allowing "junk" into the system. I also added fuel injection cleaner to the fuel tank. This may not solve your problems but its a easy solution before chaning injectors.
Good luck.