This is some info I tried to compile a while ago.....


97-03 Grand Prix
Manufacturer/Type < < < Colder Stock Hotter > > >


AC Delco

Copper 41-919 41-932 41-921
Platinum
Double Platinum
Iridium 41-985 41-101


Autolite

Copper 104 605 606
Platinum AP606
Double Platinum APP606
Iridium


Bosch

Copper 7580
Platinum 6241
Double Platinum 4304
Iridium


Denso

Copper
Platinum
Double Platinum PT16ETR-L13
Iridium IT16


NGK

Copper TR55
Platinum TR55GP
Double Platinum PTR4B-15
Iridium TR7IX TR6IX TR55IX

Platinum is not recommended for engines with power adders.


Nice info on why to run colder plugs and what it means... Spark Plug Info

webracin