Bosch Platinum plugs are very good, except when used in our Toyotas. I never believed it until I put new Bosch plugs in both my Supra and my truck and ran them for about 3,000 miles. Both vehicles started running rough and I could not believe what I saw:



The plug on the left is from the truck and the plug on the right is from the Supra. In both cases, I feared my vehicles were running extremely lean. That's one thing for my naturally aspirated truck, but certain death for the my modified turbo motor.

To make a long story short, I replaced the plugs in both vehicles with OEM Toyota plugs and now have about 6k on each. Both still run well and I pulled the plugs on the Supra on Saturday to make sure they looked okay and they looked GREAT. With twice the mileage they had about 1/3 the build-up compared to the Bosch.

Believe my results or don't. I will never use Bosch plugs in my Toyotas again.