Decades ago, the company I was with became a national distributor for NipponDenso spark plugs. A couple of years earlier, while I was a traveling salesman for the company, driving 50-60,000 miles per year in my 78 Honda Accord, I tried both NGK and ND in my car. The ND, which were original fitment, produced about 2mpg more than the NGK.
As I came to better know the ND product, my impression was not only superior quality, but a fairly aggressive commitment to technological development. They introduced several good concepts that NGK later copied.
I’ve long since retired and haven’t kept up, but my impression is that ND sort of lost the marketing war with NGK and Bosch, so they’re becoming harder to find. I turn them up on EBay as sellers try to dispose of remnant stocks. They are still original equipment on many Japanese cars.
They used to offer many optional configurations for otherwise interchangeable plugs. Gold, platinum, iridium, one, two, three, four electrodes, etc. I just installed eight NDs in my 1999 916 with 2.0 twin spark engine. Two different part number plugs for each cylinder. Running great, and cheaper than NGK.
Note, I have no complaint with NGK. They are reliable go-to plugs. I keep stock of both NGK and ND for my cars. With your presumably higher-dome pistons, I would be careful about using projecting tip plugs.
When I was the parts manager at an Alfa dealer in the 70s, the first thing our techs did during new-car prep was replace the Lodges with Champion N7Y plugs. I never heard why, but we ended up with a heap of new Lodges going into the bin.
