yea, i've had plugs for a while now. working at night, i don't wanna do anything but sleep during the day. i'll try to get up early enough to swap at least cylinder 4 out.
The 4291's. Good choice. I've been running them after the two sets of 3271's. I've yet to see a reason on any plug that I have pulled to use a colder plug in rolling 86K miles.
I have the same issue, Said screw it and bought 2 new coil packs today (autozone- 27 dollars each), NKG blue wires are in the mail also 4 Autolite AR3923 plugs. Should solve my issue.
I was running the NKG plugs............. but I followed the Mazdaspeed upgrade list and went with the Autolit racing copper plugs 1 step colder. I have a 1 CY misfire so plugs/ wires and coils are being changed before I bump up to 18 PSI
I was surprised to see you using Autolites over NGK/Denso but seeing how Mazdaspeed recommends them and they are a racing plug, guess they are worth a shot.
Best would be OEM as they last a long time. But like everything else OEM they will come with a premium. So most parts stores coil packs are your next alternative and for wires go with NGK Premium Wire Set part no 5659. Shop on line for the best prices and no sales tax.