Oh crap. What should I do?

[Mike_Yi]

Thanks for the input guys. It is definitely not speed related, but it is definitely rpm related. A coil pack makes sense. The engine does really feel like one cylinder isn't firing at all above 4k rpm. I think a plug wire would be intermittent. I'm going to pull the plugs today and see if any have a different look to them or smell of unburnt fuel. I may do a spark test on them too.

Thanks again for the input. I'm glad Jake thinks it's not internal.