Spark plug Denso or OEM Mazda

Mine came out the box .028 and I left them as is. The plugs are 1 step colder so its already a plus. The car does run smoother through the rpm and does idle smoother.

I've had a slightly rough idle since my can was new (about 6500 miles now) Got an APR stage 1 tune a few months back and of course the idle was still rough. Finally got around to replacing the stock spark plugs with the APR recommended Denso IKH24 spark plugs and..... My idle is so damn smooth now I can't even feel the engine is on. This is what i expect the idle to be like on a new car but this being my 3rd 2.0T from the VAG family i know the idle is a little rough some times.

I put IKH24's in my car as a troubleshooting step earlier this week, due to a low RPM stutter I was getting and knowing I'd been about 15K miles on my stock plugs. They made a BIG difference in my car, much smoother idle when sitting at stoplights, and running a lot smoother under boost at lower RPM's as well. No noticeable difference in engine noise. In my case, this is likely a mix of stepping to a better plug as well as my original plugs just being weary after the ocean of extra power.

kinda smoothed out the car a bit, idles smoother as well.

The coils I replaced with oem and the spark plugs Denso IKH24.

Also, did you even replace the spark plugs with Denso IKH24's? Probably not and that is REQUIRED in order to run correctly.

On 02/18/2016 I switched the plugs with the Denso IKH22 at 15800miles. Jetta is more rev happy. No slow down throughout rev range, and no more pause hesitation between 3.8k-4k RPM. Just pulls, and pulls even harder. Also idle very smoothly.

I switched to the Ikh24 and it really smoothed the car out.

Changing the plugs from bkr7e's to denso ik27's helped a bit too.

At this point it's only showing symptoms after idling for 30 seconds or more (and even then not every time), like while waiting at a stop light. Only in first gear, second and beyond have no hesitation. This evening I swapped out the almost new Denso plugs (correct gap) and the problem seems absent.