racing 12a
 

I pulled the plugs on the engine and they are NGK rm6725 11.5 but racing beat also has a plug NGK br10eix, are they similar in capability?

I've used the BR9EIX before on my old 12A. They seemed to foul out quickly for me. I use the factory type BR8 plugs on my 13b SA. Current set is about 3 years old/5,000 Miles.

There was a thread covering the topic of racing plugs a few months back in the race car section. The general agreement in that thread was that NGK6725s are a good go-to for racing and have been for years (EP, Star Mazda, Improved Touring, GT, ect). Expensive but long lasting (cleaning every so often may be needed). If you're open to the more experimental 'thin wall socket' plugs, NGK BUE (outboard 2-stroke plug, about as 'cold' as NGK offers, but risky on fouling) was also discussed.

I also know that the Spec7/Pro7 12A guys (stock engines ran as high/hard as they could go) were often using a set of 4 of the 3rd gen trailing plugs (BUR9EQP), changed out pretty regularly.

Don't forget to check/change the cap and rotor often if you are racing.