I got mine at rock auto..dirt cheap!
The AC Delcos 41-108 do have the NGK *ILTR5D* stamped on top. That's the NGK universal #for the 5476. BTW, they shipped me an 8 box and only charged me for FOUR!

 

, that's dirt cheap. picked up a pair of 6509's. NGK prefer them over the 3787's. Because of the small tip, cheap, and they fit our application with no issues. Same one's Modern Performance are selling.

 

Just ordered mine from MPx. Hoping this solves my insane misfires at WOT. It sounds like I have a dang 2-step and doesn't go anywhere lol.

 

Don't know why people are getting misfires due to plugs?
I still have my ORIGINAL stockers in with 21K mi...smooth as silk!
I do use Redline S1 fuel system treatment in every tank of gas..3oz/fill up.

 

So trifecta tune = 23+ psi should get step 1 colder NGK 3787s plugs and that do these come pre- gapped

 

you have to check them and gap them again

 

But it would be a good idea to get them for the car. Since I've done all that upgrades n what not. Bc I noticed I had a misfire once but nothing now but it sometimes idles a little rough n I asked one of my buds n he said get them bc he has them on his n says no more problems

 

The 3787s are pre-gapped to 35 already. Thats why ppl get those, so they dont have to gap them like other one step colder plugs. Of course, in practice, its always good to double check a plug that is factory pre-gapped before installing them to make sure they are correct.
Now, if you were so inclined to gap them closer, like others who claim that a tighter gap around 32 33 is better, then you would have to gap the 3787s.

 

Ok so it's a must to get them than lol

 

I dont mess with anyhting thats not broken LOL
Im still on the stock plugs. I mean, I tried one step colder plugs and went back to stockers. Engine didnt seem as happy at iddle with the aftermarket ones. Ive replaced them twice but ive stuck with stockers and I used to be on a 24psi TF tune with zero issues. Do they help a little at WOT to keep the burn cooler? Sure, maybe a little

 

i always wondered what plugs were in my 09 lnf with a gt2871 @ 24-25 psi because it never misfired ever and they are NGK BKR6ES-11. just a heads up for ppl with misfires on high boost and/or larger turbo

 

Yeah I've heard that before bout don't fix it if it's not broke, lol but everyones says it better n helps haha is amazon the only place u can get them from

 

^^I got mine from MPx

 

I have another thread started in which I explain with only GMS1, I have gone to a 1 step colder plug. Part # is 6509. From what I can tell, they were all gapped at .040. As someone previously stated, they're stiff bastards so I basically destroyed one of my many gapping tools to get them down to .035. Oh well, it sucked anyhow. Be very, very careful and use a WIRE gapping tool, as Iridiums aren't really intended to be screwed with.

Never had any misfiring issues, but as I said I was seeing 2-3 degrees of knock at WOT, roughly holding 20psi. That problem is now gone, and the car idles FAR nicer. These plugs should be more than enough to get me through the next year worth of modifications.

When they've run their course, I will be going to a copper core plug as I swear by them in boosted and high boosted applications alike. I've seen high boost vehicles literally melt platinum spark plugs before.

 

I run NGK 6510's two stages cooler plugs gapped at .030" and not a single issue yet and have had great luck with tuning with them.

 

Got my 6509's today so I am going to throw them in tonight. I guess I will gap them to .033 and see how she runs.