Could be one of the coil packs but those commonly don't have issues... did you gap the plugs right when you installed them? New wires? What brand of plugs and type did you use? Have you done your fuel filter recently? When did you do your O2 sensors and have you tried to pull any codes? No CEL does not mean there isn't a code or an issue.
2000 Mustang GT Steeda build #48. Bolt ons, suspension, Novi 2000.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.