Sometimes you should believe the error codes
When were your Series 1 (pre-cat) Labmbdas last changed?
In my experience after roughly 10years/100k miles they are usually due for replacement. Pre-cat Lambdas tell you nothing about the cat (unless its completely collapsed and blocking the pipe), that's what post-cat Lambdas are for, and you don't have those on a PF car (lucky guy!)
Since the car is telling you the injector is at fault, you could have swapped injectors with the nearest cylinder to see if the missfire moves. Personally I wouldn't be confident enough to swap injectors I have never taken one out before. There are other resistance and continuity tests you can do on injectors and Lambdas detailled in ElsaWin.