In my experience, copper performs better in a boosted environment although it doesnt last as long. This is fine because in my opinion if your modded or racing you should be checking your plugs often. Much easier to do this with a 2 dollar plug instead of a 9-12 dollar plug. Iridiums will indeed last longer and are perfect for N/A or stock inducted cars although i doubt any claims that more power will be gained by their use.

There is no power to be gained simply by changing plugs. If you gain power, you didn't have the right heat range or gap to begin with.

For a stock L67, L27, L36, or LN3/LG3, Irridiums would be great. Zero intervention. Other than you should still check them once a year or so.

But I still prefer the NGK TR55'* in my bone-stock car, simply because in a stock application, they too last quite awhile. I'm so used to changing plugs in the Zilla 3 or 4 times a year, that changing them once every year or two in the other car means little to me.

Keep in mind, some of the highest achieving MPG'* on this Forum were done with TR55'*.

This is odd. I found a different parts list for the same vehicle at Advanced Auto Parts online (using his link).

You listed 15 parts, my search came up with 25.

There are also major differenced in pricing! The AC Delco Iridium on his list is $11.99 each, but mine is $6.96. That'* a HUGE difference in price!
FWIW, RockAuto.com has them for $5.53 each.

On the other hand, Autolite XP'* (this thread'* topic) are $5.99 at his location, and $6.48 in my area. 50 cents may not be enough to make a big deal over, but we both can order these from Advance mail order, so theoretically we should get a comparable price, except maybe for shipping.. (RockAuto.com has these for $4.82, but only sells them in 4 packs)

I wonder if it'* a difference in regions? My Zip is 27519, Cary, NC. Maybe that'* the difference? RockAuto doesn't ask your Zip Code before telling you the prices because it'* strictly mail order. This has been interesting! Thanks to everyone here!!!!

Here'* my list from Advanced Auto Parts online (same link as his, same car, but using my zip code)

For vehicle: 2000 BUICK LESABRE CUSTOM V6 3.8 Liter FI (change)
25 parts found.

Part No.
4459
Bosch Spark Plug: Platinum+4; Price Is Per Spark Plug
Spark Plug: Platinum+4; Do Not Gap
Warranty: 3 Year Replacement Warranty
$6.97

Part No.
4304
Bosch Spark Plug: Platinum 2; Price Is Per Spark Plug
Spark Plug: Platinum2; Do Not Gap
Warranty: 3 Year Replacement Warranty
$4.97

Part No.
4504
Bosch Spark Plug
Spark Plug: Platinum IR Fusion; Do Not Gap. Gap Is Not Adjustable.
Warranty: 3 Year Replacement Warranty
$9.98

Part No.
4041
Bosch Spark Plug
Spark Plug: Platinum Plus; Gap 0.060"
Warranty: 1 Year Replacement Warranty
$2.98

Part No.
6241
Bosch Spark Plug: Platinum; Price Is Per Spark Plug
Spark Plug: Platinum; Gap .060
* Not currently available

Part No.
7580
Bosch Spark Plug: Super; Price Is Per Spark Plug
Super Plug: Oe Plug Is Platinum; Gap .060
$1.19

Part No.
7580
Bosch Spark Plug: Super; Price Is Per Spark Plug
Super Plug: Original equipment plug is platinum; Gap .060
$1.19

Part No.
APP606
Autolite Ignition Spark Plugs: Double Platinum; Price Is Per Spark Plug
Premium Spark Plug: Double Platinum; Gap .060
Warranty: 5 Year/ 50,000 Mile Warranty
$3.97

Part No.
AP606
Autolite Ignition Spark Plugs: Platinum; Price Is Per Spark Plug
Premium Spark Plug: Platinum; Gap .060
$2.69

Part No.
XP606
Autolite Ignition Spark Plug: Xtreme Performance
Premium Spark Plug: Xtreme Performance; Oe Style; Gap .060
$6.48

Part No.
606
Autolite Ignition Spark Plugs: Copper Core; Price Is Per Spark Plug
Standard Spark Plug: Gap .060
Warranty: 2 Year Replacement Warranty
$1.48

Part No.
41921
ACDelco Spark Plug: Professional Platinum; Price Is Per Spark Plug
Platinum; @ Gap .060" @
Warranty: 3 Month Limited Warranty
$9.99

Part No.
41101
ACDelco Spark Plug: Professional Platinum; Price Is Per Spark Plug
Iridium; @ Gap .060" @
Warranty: 3 Month Limited Warranty
$6.96

Part No.
3013
Champion Spark Plug: Platinum Power; Price Is Per Spark Plug
Platinum Power: Gap .060
Warranty: 1 Year Replacement Warranty
$2.98

Part No.
7013
Champion Spark Plug: Double Platinum; Price Is Per Spark Plug
Double Platinum: Gap .060
Warranty: 1 Year Limited Warranty
$4.77

Part No.
13
Champion Spark Plug: RS14YC6 Copper Plus; Price Is Per Spark Plug
Copper Plus: Rs14yc6; Gap .060
Warranty: 1 Year Replacement Warranty
$1.77

Part No.
9404
Champion Iridium Spark Plug
Iridium Spark Plug: Gap .060"
Warranty: 1 Year Replacement Warranty
$9.88

Part No.
3403
NGK Spark Plug: Plug No. TR55GP
G-Power Platinum Plug; TR55GP; @ Gap .060 @
Warranty: 2 Year Replacement Warranty
$2.98

Part No.
7164
NGK Spark Plug: Plug No. TR55IX
Iridium IX Plug; TR55IX; @ Gap Do Not Re-Gap @
Warranty: 2 Year Replacement Warranty
$6.96

Part No.
5146
NGK Spark Plug: Plug No. PTR4B-15
OE Style Laser Platinum; PTR4B-15; @ Gap .060 @
Warranty: 3 Month Limited Warranty
$9.98

Part No.
5599
NGK Spark Plug: Plug No. ITR4A15
OE Style Laser Iridium; ITR4A15; @ Gap .060 @
Warranty: 3 Month Limited Warranty
$9.88

Part No.
3951
NGK Spark Plug: Plug No. TR55
V-Power Plug; TR55; @ Gap .060 @
Warranty: 1 Year Replacement Warranty
$1.77

Part No.
E362
E3 Spark Plug
@ Do Not Gap @
Warranty: 5 Year Limited Warranty
$6.96

Part No.
8176
Accel Spark Plug: U-Groove; 6 Pack; Price Is Per Spark Plug
U-Groove Resistor Blister-Pak; Spark Plug: 6 Pc. Of Pn0526:
Warranty: 3 Month Limited Warranty
$15.99

Part No.
P526S
Accel Spark Plug: U-Groove; Price Is Per Spark Plug
U-Groove Spark Plug; Header Plug: Double Platinum Shorty
Warranty: 3 Month Limited Warranty
$12.99

yeah spark plugs are like tires and everything else on the car. Everyone has their own opinion of whats best for them. I know what works for me and I get over 100k out of my plugs by only filing and re-gapping the tips every 30k.
Take note of the Bosch warning. Everyone has had the same experience on the forum...

Actually I don't mind spending money on new plugs, bosch or whatever, every year. I do have a small sandblaster that I can use to clean off the tips if I wanted, but would rather put new in. So if the Bosch+4s start to go bad after 8-12 months, I don't mind.

I will probably, for argument'* sake, try the NGK TR55s the next time I swap out plugs. We'll see how they work. I just want to make sure it'* still got the power it has now.

Is that ALL Platinums or just Bosch Platinums?

Right on the money. Even my 98 Z71 and 94 Suburban ate Bosch Platinums for breakfast. In just a couple months.