Spark plug Bosch or Denso

My 2017 VW Jetta 1.4 5M - at 67760 miles on the factory original plugs - now has new Bosch Iridium/Plattinum plugs - (YA5KIP80)..................(the only symptom on the old plugs was a MPG drop - no hard starting, no missing, no rough idle......... EZ

changed out the spark plugs, all except for cyl 1 had crazy looking plugs. Used Bosch platinum 6704 cleared up the CEL and also the stability and TC lights no longer flash so somehow that was connected I guess.

Denso work quite well

For iridium spark plug. Do NOT gap them. I have bosch double iridium spark plugs and over 120K miles now. Still goes strong.

My car has Bosch Double Iridium spark plugs. Over 120K miles now still go strong.

Bought some Denso 3450 Irdium plugs online. After reading about counterfits. I decided to test mine.

All are gapped .43 for the OEM spec for a 2014 Nissan Xterra. I measured the Irdium electrode tip which is 0.7mm and appears blue

I ran Denso iridiums for 100,000 miles on mine, they looked usable when I pulled them. Replaced them with NGK's, no difference in power generated.

Neither, I’ve seen Bosch plugs fall apart and I wouldn’t trust autolite on my lawnmower.

Installed new Bosch Plugs (WR7DC+), Bosch Distributor Cap, and Rotor. Now the car seems to be having a weird idle sitting as stop lights, and the engine almost shut off while I was backing into the garage. Also she seems like its having a harder time sterting up as well.

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.