Get past plugs, and then check the old ones for condition. You can get a spark plug condition diagram online. I've used Seafoam in conjunction with the gas tank as well as throttle spray to clean the upper intake and the fuel line on forward. If all fails, go back to see if the spark plug boots have any small tears or anything like that. There will be spark on the block that you cannot see within the plug chamber. Other things will cause it, but more indepth.

Nothing but headache with champion plugs, prior to that I was using ngk v power no rough idle no miss fire , I switched to champion and rough idle and miss fires

Not really. The voltage and timing is not set for the iridium but they do work and tend to get pre-detonation or burned after 60k for inspection. You won't gain much and in my experience slinging parts most of the Jeep folks attest to Champion coppers on the inline 4.0's. Some go platinum, but depending on the wear of the engine's age, the champ coppers are the way to go. The iridium's are thin wire, more for direct and demanding systems for spark, gas injection, and vvt changes for timing on newer vehicles. I have run them but changed them out to copper plats after a seafoam cleanup.

Is it a good idea to put Antiseize on the plug threading?