[Icanfixit]

Hi, how did you find out it might be an injector issue. If only a guess, a small misfire at 6000 rpm could be a coil on its way out.

 

[Icanfixit]

When removing the coil/spark plugs to test - did you test it at the 6k rpm like when it does misfire. I hate misfire issues too, but have learn’t it may be a other causes beyond the obvious. Hope the clean clears it up for you. Good luck