I bought my '08 SS with 12,500 miles on it roughly 3 months ago. I had the GMS1 tune installed the first week I had it. A few weeks later I noticed a misfire under load. After doing some reading on this site, I determined I needed to run a plug that was 1 step colder than stock.

After a few weeks of running the 3787's the car still suffered from a random misfire under load. I was tinkering around under the hood one day and noticed the bolt for the TMAP on the cold-charge piping was loose. The sensor was flopping about at will. I tightened it down and continued to run the 3787's.

The car still had a hesitation or misfire that was so random I couldn't pin it down. I didn't think of the plugs and left them alone for the last few weeks. Tonight I changed the plugs back to stock and did a few hard runs on the street (60 mph speed limit, ran to 80+). The car pulled hard and had no hesitation or misfire whatsoever. I live in Salt Lake City, Utah and am about ~4200 feet. The GMS1 produces around 24 psi peak, and holds roughly 22 psi.

Every car is different, and every driver is different. I'm not saying a step colder will be wrong for you, but for me, and the GMS1, it wasn't good. My issues were with a loose TMAP sensor. The boost leak caused a hesitation and misfire under load and was not the spark plug's fault.

I'll keep the factory AC delco plugs in and give an update after running them for a while.

 

Ive also been wondering about the need for new plugs with my Stage 1 with Custom tune over it

 

So is it best to stick with the stock plugs, I need new ones mine are gross looking

 

3787's running fine with mucho boosto here.

 

So I should go with them, or stick with stock. Once I get my issue figured out , Im going with trifecta tune.

 

If you are going to up the boost, get the 3787's. They are 1 step colder than stock.

 

yep thats what I did and the car loves it!

 

 

15k miles+3787's+hpt+recent gms1+lots of boost and the car's loving it. <shrug>

 

1 step colder didnt work for me, car hated it

 

Im trying the XP5632s right now (Im pretty sure thats the number lol..)

 

Definitely not the number

Tell me which ones you got and I'll try em out as well, just annihilated one of my 3787's.

Xp5263? Maybe the XP5364's?

 

Ill check the box in teh garbage on my way out this morning and post back in an hr or so. I believe it was the 5263


Yup, XP5263's.

Autozone by me also had the factory 1 step colder plugs: 41-105

 

You should also try Denso Iridiums ITV16 0.4mm they are also 1 step colder. http://www.densoiridium.com/ I had them onced in my 07 SS/SC w/o issues.

 

I'm gonna snag a set of the XP5364's and see what happens, since they're gapped just like the 3787's and don't have the long tube ****.

 

Just picked up some Xp5263's today.. only thing I could find locally here in Canada, other than GM of course, so gonna try em out tomorrow.