I recently had a brand-new, out of the box, Bosch cap that was defective. Looked perfect - still does. Measured fine via ohm meter. Only caused an intermittent misfire at hot idle, zero issue under load, at WOT, or above 2k. Drove me absolutely batty trying to diagnose it and took about 5 hours total time. Don't think I will be buying Bosch caps again, for $90 each I expect new ones to actually, you know, WORK.
Dunno what the best alternate brand is, or if OE (likely Bosch as well) would be any better kwality.