Spark plug Bosch or OEM Toyota

Unfortunately no--replace them. The electrodes wear down and become less efficient. The good news is that iridium plugs have a tremendous lifespan. You're supposed to change them every 100k miles/167k km.

Since I mounted Bosch 4-prong spark plugs, fuel economy has improved a lot. Gone from 12-13 km/l to nearly 15 km/l.

I have only used Bosch plugs in my cars, and I have not had any issues with them yet.

Bosch iridiums, these for longevity, copper ones have better spark if your concern is performance

Today I installed new spark plugs and the misfiring situation has improved significantly but is not completely gone. If I pull up the RPM too quickly the misfire counter goes up.

The Neuspeed chips don't perform well at all, and the 2.0's do best with BOSCH FR8DS's.

Just got a Jetta again - 2010 Limited Edition just shy of 100K miles and I've got one problem with it. From a cold start, usually in the morning, the 1st 10-15 seconds run rough before settling down to idle.

I've heard for many decades how bad Bosch spark plugs are and I figured the coils would be just as bad, if not worse.

Bosch spark plugs are junk.

This is why I don't use Bosch plugs. It goes back to the quad fire plugs with a platinum center electrode that would fall out.