I have for the most part over the years used Bosch in my autos, American & the 1 Mitsubishi I had. But within their line I found that the cars are happier with the Copper core plug (Super plug) than the Platnium. I will admit the Platnium plug runs the engine a little smoother, but I get beter performance with the copper plug. I've had a few Fords, a few GM'* ('70 Chevelle, '97 Boneville and a Chevette - don't tell anyone) and the one Jap.

The Bonneville had the GM iridiums in it, I just recently replaced them with the Bosch Super, didn't have the cash to spare on the pricer plugs right now.

What I want to try, when Champion comes out with them is their Premuim Gold Iridium plug. Supposed to have a coper core with a iridium/gold tip. Will be a killer plug. But I haven't seen them available at a retial level yet.

I've never found a big difference in wires, but then agin I haven't had the spare cash to lay down for $50+ wires. Always been content with the Bosch wires. That'* what the Auto stores in the area carry mostly. Have tried generic, didn't see a diff to speak of.

OK THE SCIENCE LESSON

In general the electrical conductivity of copper and iridium are far superior to platnium.
But platnium and iridium have a better durability than stright copper. And gold has a durability up there with platinum (a little better actually) and electrical conductivity near that of copper. Hence Champions idea for the Gold Iridium line, with th copper core.

So don't get to hyped on Platinum as the best plug:
If you want long term durability- Platinum.
If you want a little better performance and don't mind changing the plugs once in a while go copper.
If you have the money go the iridium route, they use a copper core and have good performance.
Brand loyalty is upto you.

Good luck.

Thanks to everyone that replyed.

My 90 SSE has Bosch platinums. I absolutley love um. Mileage went up 2 MPG!
My 96 SE has Delco platinums it gets poor city mileage 15 - 16 MPG.
Bosch uses a pure platinum electrode which will self clean a lot faster than copper.
So if you do mostly city driving its the way to go.
Delco uses a copper core with a platinum tip. I never liked this combination.
I just removed them from my 96 and put in Bosch Platinums.
Two of the six Delco plugs (#2 & #4) were dark in color at the tip with only 10 k on them.
I'll let you know in the next few weeks if it cures my mileage problem around town.

If your plugs are dirty, or fouled that may cause the bad milage. Also something else could contribute to bad plugs AND milage.

I hope its not oil leaking through the plastic intake.
Time will tel with the new plugs.

Well.. researching around a bit.. ( mind you it'* internet.. there'* a lot of good and bogus stuff ).. as for wires, if you're not going to heavily modify the snot out of your car, OEM wires and coil packs are supposedly way to go.. but again.. thats from net research.

As for the plugs I wouldn't say they were fouled. Just two of them were not
chalky white like the rest. Maybe they were not running as hot as the rest or
those two wires had higher resistance. I'll check it out when it gets warmer out here in CT. If the mileage goes up in the next few weeks I'll check nothing.
Thats my new motto. If it ain't broke don't fix it!

Also don't forget in determining the mileage of your plugs the 3800 engine
uses a "waste spark system". In other words to fire the #1 plug the two wires
connected to that coil spark at the same time.
The #1 fires the cylinder and the other is wasted. Thus the term waste spark.
It takes 12 sparks to fire 6 cylinders.
So if you think you have 10 k on them think again. It could be more like 20 k
actual detonations.
So if a plug is designed to last 30k its a real stretch on the 3800 engine.
I use Bosch HR9DPY stock 6241platinums that I don't expect will last the whole 60 k. Its like 120 k actual use.