From NGK's web page
6. Using "racing" spark plugs
Be cautious! In reality, most "racing" spark plugs are just colder
heat ranges of the street versions of the spark plug. They don't
provide any more voltage to the spark plug tip! Their internal
construction is no different (in NGK's case, as all of our spark
plugs must conform to the same level of quality controls) than
most standard spark plugs.
There are some exceptions, though. Extremely high compression
cars or those running exotic fuels will have different spark plug
requirements and hence NGK makes spark plugs that are
well-suited for these requirements. They are classified as
"specialized spark plugs for racing applications". Some are built
with precious metal alloy tips for greater durability and the ability to
fire in denser or leaner air/fuel mixtures. However, installing the
same spark plugs Kenny Bernstein uses in his 300+ mph Top
Fuel car (running Nitromethane at a 2:1 air/fuel ratio and over 20:1
dynamic compression) in your basically stock Honda Civic
(running 15:1 a/f ratios with roughly 9.5:1 compression) will do
nothing for you! In fact, since Kenny's plugs are fully 4 heat ranges
colder, they'd foul out in your Honda in just a few minutes.
NGK as a company tries to stay clear of saying that a racing spark
plug (or ANY spark plug) will give you large gains in horsepower.
While certain spark plugs are better suited to certain applications
(and we're happy to counsel you in the right direction) we try to tell
people that are looking to "screw in" some cheap horsepower that,
in most cases, spark plugs are not the answer.
To be blunt, when experienced tuners build race motors, they
select their spark plugs for different reasons: to remove heat more
efficiently, provide sufficient spark to completely light all the air/fuel
mixture, to survive the added stresses placed upon a high
performance engine's spark plugs, and to achieve optimum
piston-to-plug clearance.
Some of these "specialized racing plugs" are made with precious
metal alloy center/ground electrodes or fine wire tips or
retracted-nose insulators. Again, these features do not
necessarily mean that the spark plug will allow the engine to
make more power, but these features are what allow the spark
plug to survive in these tortuous conditions. Most racers know
screwing in a new set of spark plugs will not magically "unlock"
hidden horsepower.
Knowing that go here to find the spark plug that fits your application.
Read more here