Motor Misfires After Spark Plug Change

I recently changed my plugs in my 2008 gt 4.6. Broke the plug on the rear drivers side. Got that out and when I started it had a bad idle. Took it to ford and they said it was catalytic converters. Replaced the converters and still misses. Checked fuel pressure it's around 30 to 35 lbs. Checked coil packs with old spark plug and they fire. Used a sthescope on each fuel injector and can hear them click. Can't get a code to read on 3 different plug in computer. Took it back to ford and they said it was mufflers. Took flow masters off to make sure they wasn't any blockage. My new spark plugs have black carbon on them.

Thanks timjimmy. The new spark plugs are sp 514. Can you gap them plugs. OReilly said they would take back plugs and give me the original ones.

Thanks i solved the problem. I took back the new plugs i bought at OReileys. Bought some new plugs at dealership put them in and it runs like a top. Can't believe my whole problem started with new plugs. Plus dealership couldn't figure it out. Thanks for ur help.