It's probably not the plugs, but I would definitely replace them with new Chamion Coppers. They're what the 4.7 V8 likes. Do some searching if you want to confirm. It will probably like the cheap Coppers more, but again, that's probably not the actual problem. I'd do some searching and checking on this forum when replacing any part or doing any repair, really, cause the V8 is so finicky and particular about things. It's good to find out what's really recommended.
3.5" lifted '03 Limited Quadra Drive WJ - OME HD coils, Bilstein 5100 shocks, JKS track bar, IRO extended links, OME 10mm spacers, Moog SS, JK Moab wheels w/ 265/70/17 (32") Goodyear Duratracs.