Spark plug NGK or OEM Mazda

You can check the forums and it'll say the same thing your asking . It comes down to personal reference ,everyone (including myself ) that I run with in our 3rd gens we run NGK . Just make sure they are dual pronged and gapped correctly and you'll be just fine .

Use NGK iridium and you will have no problems.

I went with NGK iridium's. The "book" says they should be replaced at 100k. I mostly didn't want to have to fight with them at 100k miles to get them out.

I run usually one of 2 brands. Brisk or NGK both iridium. And both are 1 step colder than stock.

Last time I went Bremi coils and NGK Laser Platinum plugs.

Installed the NGK rs7 plugs and it runs fine. I kept them at factory gap, which was, if I remember correctly approximately .028.

I just hit 40k miles and went with the NGK (RS7) plug gapped to .024, and the RS3 coil pack upgrade. The initial results after install was underwhelming. Car ran a tad smoother, but that's it. Since the benefit of the RS3 packs were to provide a more intense spark, I tried a wider gap ~.028-.030 Man it woke things up! Revs "effortlessly" and pulls hard from top to bottom.

Bottom line: you can't go wrong with NGK. Can't really go wrong with OEM Bosch either but I'd just stick with NGK and make sure you gap them right, call it a day. I'd avoid Denso.

I'm running PFR7Bs. I get a misfire or 3 here and there, only during low load low speed acceleration. I've got R8 coils too. Not sure if the RFD makes them occur any more frequently than they otherwise would, but I'm not worried about it.

I used the NGK plugs once and kept getting a pretty bad hiccup under hard acceleration.