2002 XK8. Had misfires on 7 & 8. Switched coil from 8 to 5 and 7 to 6. Now just pending code for misfire on 5. I think I’ve heard yes to question above. Thoughts?
Probably just order two in any event to have an extra around. I’m not one of those guys who believes in changing every coil when one goes bad.

 

Maybe/probably - it's hard for it to detect and diagnose misfires.

If you swap, keep the old ones in case the new turn out worse...

 

before you fit blow out plug recess with compressed air ....my misfires caused by water around the plug.

 

Check for oil there, too.

 

It uses the crankshaft position sensor to calculate crankshaft acceleration and therefore detect a misfire and which one it was. That should be pretty accurate.
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Since all your misfires are on bank 2, one way to tell who could be at fault is to mark all 8 coils with a marker for their cylinder ID and swap them from one bank to another, clear the codes and test drive it. If the misfire(s) move with the coil swap, you’ll have your answer (hopefully). I know these cars can be finicky at times though.