You've changed plugs, made sure they're gapped properly?? BOSCH or NGK is all I use. Iridium or platinum. I've not had many issues except the 'hiccup' you can feel at idle with all of these things. Notorious I'm finding. Could have gotten some that werent pre-gapped or gapped incorrectly. I've done that from Orileys, gotten poorly gapped plugs which were to be pre-gapped. Coils, fuel filter, MAF? Never know what could possibly be coincidence. I've had happen WAY more than once with coincidental shit happening.