Spark plug Bosch or OEM Mazda

the spark plug is less than 10k km old (bosch) so I initially did not change it. Decided to change it anyway to original mercedes (turns out made my NGK) bam emission passed, LTFT now hovers at 5-8%.

I've changed my spark plugs three times, always with the Bosch Iridium, never had any problems. Pre-gapped, takes me about 30 minutes from start to finish. Lasts me about 90,000 miles.

The new ignition switch is in. The spark plug wires are Bosch copper and now have the Bosch super 3 ground electrode plugs installed. So with a fresh ignition switch that eliminated the odd electrical changes we were seeing in the dash lights, now stronger cranking and it does run better.

Bosch W6DPO. They’ve always been expensive, but now stupidly so. I’m not paying $250 for plugs, either. The DENSO IW20TT you referenced is a perfect replacement because it’s the exact same heat range as the W6DPO.

That said, make sure they use quality parts. BMW/Bosch spark plugs and OEM pulleys (and belt) are a must. NGK plugs are cheaper and don\u2019t last as long. Same goes for off-brand belts and pulleys.

I have used NKG FOR THE PAST 6 years on the car , no issues at all. Recently replaced them with Bosch OEM spark plugs , it’s same shit , no difference.

Bought mine from rock auto; got the Bosch ones since the NGK’s are really only recommended if your car is tuned

definitely avoid Bosch spark plugs. I'm not personally a fan and I've seen plenty fail. Unless they were original in the motor (usually Subarus don't use Bosch), I'd stick with NGK or Denso in my opinion.

Bosch spark plugs are also trash.

Those spark plugs are junk, and on top of that, they are now carbon fouled. I would strongly encourage you to install new, normal, spark plugs.