If something runs bad, and you substitute what is known to work well 100% of the time, with something not even designed, by heat range, or gap/performance for your engine, its hard to gather conclusive results. Everyone throws the name premium around, like they all claim to be mechanics. Premium is what works best in a given situation, and what is claimed to be premium, may not really be. The iridiums work differently yes, and the gap is different, but the demands for ignition coils are different as well. Those plugs may fit several different vehicle brands, and what a chrysler needs, will not be the same as what toyota needs. Thats why you see GM wants 0.060" for plug gaps on some, chrysler likes .035, or .040 on some, and ford likes .044, .052, .035, etc. If you are having a running issue, if you want to save headaches and money in the long run, put what should be in there first, and get it running right. Then play with the sparkplug of the month, or what have you. You'll spend less time chasing your tail.