Who sells NGK 4930 (BCP6ES)? Summit says they have been discontinued.

Try Google

I did and a lot of websites says discontinued.

Yep, almost all or everyone that I searched (Amazon, ebay, motorcycle, ATV parts distributors, etc.,) say NOT AVAILABLE??

i just bought 8 yesterday from Advanced Auto.They were in stock.

Napaonline.com shows them available

Ebay shows lots of listings

Thanks. Going to Napa today to see if they have them.

Try BCPR6ES.

Same specs but has a resistor.

I got the last 16 from Napa.

What is the difference between a resistor and non resistor?

unless the application is an all out race effort, resistor plugs will work fine.
just choose the heat range that will work the best for a particular combination.

On my race bikes I try to avoid a resistor spark plug. Cars and motorcycles have been coming with a 5k ohm resistor spark plug caps for a long time and I see no reason to add in more spark energy resistance. Maybe if my AM radio starts to have RFI then and only then would I run an additional resistor in the form of a resistor spark plug. Just me.

Superceded to a 2330 stock number. Same plug.

No. 2330 is the Resistor plug.

WHAT IS A RESISTOR SPARK PLUG?
Spark Plug Resistor Location

At the moment the spark jumps the gap it causes a high frequency burst of energy, known as RFI (radio frequency interference). RFI, as its name suggests, creates static on your radio and interference with other electronic equipment, including the vehicle’s on-board electronic control units (ECUs).

Resistor plugs were developed in the 1960s to suppress some of the spark energy, thus lowering RFI to an acceptable level. Most resistor spark plugs use a monolithic resistor, generally made of graphite and glass materials, to filter the electrical voltage as it passes through the center electrode.

Since resistor type plugs actually “resist” some of the spark energy, non-resistor type plugs actually deliver a more powerful spark. It is for this reason that most racing plugs are non-resistor types. However, in most automotive applications, a resistor plug is required for proper vehicle operation. Use of non-resistor plugs in vehicles that call for a resistor type can result in rough idling, high-rpm misfire, and abnormal combustion.

You can buy direct from NGKs website if they have them:

https://www.ngk.com/ngk-4930-bcp6es-nickel-spark-plug

Says Discontinued, and to use NGK 2330

https://www.ngk.com/ngk-2330-bcpr6es-nickel-spark-plug

As you increase the ohmic resistance of the sparking system,
either by adding a resistor to the spark plug
or adding resistance to the wire,
the “burn time” of the spark increases.

Having a very intense spark with high current but for very short time,
by experiment has been found to result in more “misfires.”

Lowest misfire rate happens at the compromise where the spark intensity is “good enough” and when the time the spark endures is relatively long,
by experiment has been found to result in lowest possible misfires rate,

At high rpm a single coil does not have time to “recover” before the next cylinder fires.
Misfire rate at high rpm can be reduced at by having a coil for each cylinder.

Misfire rate can be further reduced by having two (or more) spark plugs per cylinder, each with its own coil.
( 5.7 Hemi set up)

Seems excessively crazy,
but an MIT student wrote his Master’s thesis about finding how many spark plugs per cylinder were needed to reduce the misfire rate to zero.
He got up to 16 spark plugs on a single cylinder and was still finding improvement.
The single cylinder, variable compression ratio, side valve design, CFR engine he was using has a combustion chamber design that lacks modern “overhead valve” engine design with quench, swirl, or tumble.

Your MIT example negates your increased resistance claim.

As you add resistance in parallel ( more plugs in this case) over all resistance drops.

You need to cite both claims to make a coherent conclusion.