The argument of Mazda R&D is total bullshit@!
If it was good then you would tune your own car to 10.0:1 AFR at 200bhp level LOL! like they do? have you ever tested a bone stock FD3S, I have I list the data which no one else does!................ Just cause it came from a mass produced factory does not mean its right or the correct, that argument is spurious at best.
Done believe me go instrument a car and change out these rubbish plugs for a set of B9EGV's and post back. You will find it will use less fuel, make more power, be less sensitive to over rich (OEM is best tuning) ....... I could go on and on.
I did all of this testing in the mid 90's a long time ago, like I said I forgot just how bad these stock plugs are, have not used them in a very long time and every time I change them out and do nothing else (don't tell the customer) they all give feedback on how much better the car is, that is not placebo either as most are very anal and know their cars intimately and if there was any negative I am sure they would tell me about it
Try it Ted, if I am wrong then I am happy to be told so, by you or Mazda, but I am not and never am.