OEM. there have been so many times at work that someone will come in with a random misfire with brand new non OEM plugs, changing to OEM plugs makes the misfire goes away.
I've got autolites in my car. The copper ones only last around 15k miles but at $2 I don't care. I like the copper because it extracts the heat better (more important in my car than yours)
These are what GM switched to for the later ~'03 models anyway, so it's not going to cause any problem. The original style will with falling off ground tabs.
AC plugs are also all NGK (or Autolite in many cases) because the AC Spark Plug plant in Flint, MI doesn't exist anymore. It was closed a couple years ago IIRC.
Brenden you cannot simply go wrong with any of the following spark plugs, all will last long, and last well, perhaps you should decide on the basis of best price you can find!
NGK Iridium IX
Bosch IR Iridium
Denso Iridium Long life
NGK ir/plat, Denso ir/plat, Champion ir/plat, AC Delco ir/plat, Autolite XP are all good. be sure to CAREFULLY check for bent electrode and GENTLY check the gap.
For my own 3.4 I used the AC Delco ir/plat; they work perfectly, and they should last 100,000 miles.
I generally stick with the OE brand/part. Ive found this to generally be NGK across a variety of manufacturers, though certainly not the rule.
I tried autolite iridiums in place of the delco (I think they are denso actually) dual platinums that were OE in my truck. I think they are quie good, and may consider the iridiums for other applications in the future...
Originally Posted By: beast3300
For the 3400, go with stock Iridium AC Delco.
See that's the problem with the originals. Although GM upgraded to iridiums and started using a NGK/Denso for later models they still supply the old style ACDelco double platinums for earlier models. So if he goes with the NGK laser iridiums he would be getting the same as the updated ACDelco plugs.