Detonation?
 

What does detonation feel like? From say 2500 rpm and up when cruising, The car feels like it misses, like it is a cylinder missing, but doesn't do it (noticeably) at WOT. Could this just be a result of not having a tune?

Detonation is more easily heard than felt in most cases. There is a definite drop in power, but it shouldn't feel like a miss (since every cylinder should be basically identical).