They fixed it...booo :(

FYI -

I ran the NGK iridiums.

7-8K miles

Got antsy and swapped back in new 4 prongs.

Made it about 500 miles before I put the iridiums back in.

Once you put the NGK Iridium in, you don't ever want to go back to the Bosch 4-prong thingy...

Why not use a multi-electrode plug?

Multi-electrode plugs reduce the percentage of misfires by using surface gap technology (longer spark path) & multi spark paths. Due to less then perfect fuel/air mixtures (lean/rich areas in the combustion chamber) a single gap plug allows for more power strokes without ignition. From what I've read, single electrode plug fired gasoline engines have unignited power strokes of 4% to 5%, 4 electrode plugs reduce that to around 1%. They also require less voltage to fire due to surface gaps (the spark jumps across the insulator surface where there is lower resistance.

An additional downside to single electrode plugs (when in central position of the combustion chamber, BMW motors) is the fact that the protuding electrode blocks the flame kernel path to the center of the piston, reducing power/fuel economy.

With plugs positioned to the side of piston center, a common practice is to index the plug, to face the flame kernel path at the center of the piston face. HP/TQ gains of 2% to 3% on dyno tests after spark plug indexing are common.

QUOTE>>>>"Spark plug manufacturers have succeeded in extending the life of spark plugs and fouling resistance by going to high-temperature electrodes made out of platinum, iridium and other exotic metals. Platinum is one of the best conductors of heat and electricity. It also resists chemical corrosion and electrical erosion much better than ordinary steel alloys, making it an ideal material for the electrodes in long-life spark plugs. Iridium is even better. Iridium is six times harder and eight times stronger than platinum. This allows the use of a smaller center electrode, which reduces the voltage required to fire the plug by as much as 5,000 volts compared to a standard spark plug.
Spark plug manufacturers also use a variety of different electrode configurations to reduce misfires by exposing more of the spark and flame kernel to the fuel mixture inside the combustion chamber. Extended electrodes, surface gap electrodes, multiple electrodes and specially-shaped outer electrodes are all different techniques that are used to improve ignition performance and reliability."

AND

"One way to reduce misfires under load and improve ignition reliability is to expose more of the spark to the air/fuel mixture. Standard electrodes tend to shield the spark somewhat and can actually quench the initial flame kernel under some operating conditions. To open up the spark, some spark plug manufacturers split the tip of their outer electrodes."

Here.....

Questioning Misfires | Tomorrows Technician

Bosch Platinium Iridium Fusion 4 electrode plugs are about $5 each. Just installed a set a few weeks ago........

BoschLive - Archive

Once you use NGK Iridium plug, you don't look back at the Bosch 4-prong thingy.
Never.

Again, why?

I'd be wary of any anecdotal evidence that one plug is better than another. Most people change their plugs because the old ones need changing. Of course the engine will run better. The engine would run better with new plugs of the same type as the old ones.

TiAgX5 quoted differences in the <2% range. I doubt that anyone would be able to feel the difference or notice a change in fuel consumption in normal driving.

I used Iridium's when I raced, and yes, I indexed them. Good plugs.

I forgot to look for them when I put new plugs in the X5. I put in the bmw quad electrode ones replacing single electrode plugs and my mileage has dropped by 1 mpg or so (small sample statistics, I know)...

I installed the OEM and they cost $22 apiece , end no magic.

Read the "comments" on this link.