i only had misfire when car was hot and revving above 4000rpm. Just like how you described. Removed coilpacks, inspected and looked visually fine. (no cracks etc). Mechanics were telling me its not coilpacks either.
Ended up replacing with brand new splitfires and problem was gone.
Unless you have tested with a brand new set of coilpacks, i wouldnt rule them out just yet...