Plug gap is relative to your ignition system. A tune is not going to be relevant to plug gap. If you're running iridium plugs DO NOT gap them, you'll break the electrode. If squashing your plug gap (below factory recommendations) improves your drivability then you have a failure in your ignition system and may want to look at new coils.

The spark plug gap affects the voltage required to jump the gap and actually light the air-fuel mixture in the cylinder. A larger gap requires more voltage. Increasing gap size can actually lead to a more efficient burn since it increases the spark area. However, high cylinder pressures (compression ratio & boost) can blow out the spark if the gap is too large.

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However, they’re still generally good guidelines to follow. The more boost and heat you generate the more heat you need to move away from the firing tips. There isn’t much need or reason to go overkill and get too cold of a spark plug, either. The following is a specific list of our spark plug preferences:

So here are some questions I have, and would like to hear any other observations people have as well: Please note – power numbers below are rough estimates of where we like each spark plug. For example, some run OEM N54 spark plugs above 400whp without issue while others like to run the NGK 2-step colder spark plugs even at 350-400whp. If your current spark plug setup has been working then there’s not much reason or benefit to changing things. However, if you’re planning to add more power then it is usually a good idea to start considering higher quality, colder spark plugs. The ceramic insulation for the ground electrode on the 97506 is 5mm wide inside the steel shaft, versus 3.8mm for the 95770. Can you speak on the impacts of running WMI and how that relates to the spark plug setup? Does WMI sufficiently cool the engine enough to make up for a full 1 step colder? What about gap sizing? I'm going to try to be as brief as possible but there are several related things I wish to bring up relative to plugs. I've done reading on Spoolstreet as well as other forum threads, with some success, but nonetheless ...

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All spark plugs remove some heat from the plug tip and transfer that heat to the engine cylinder head. Colder spark plugs are faster and more efficient at transferring heat away from the spark plug tip. Basically when you hear cold plug it means the spark plug transfers heat away from the tip rapidly. Hot plugs are slower at transferring the heat, which means the firing tip remains hotter. Moving over to a 1-step colder NGK spark plug did seem to help clean up timing and misfires became less common. Exact results can vary from car to car. Still, the OEM plugs can start becoming more problematic too far beyond 400whp. If you’re around that number and aren’t having issues then there isn’t much reason to change things. Which spark plug is right for each person, engine, mods, tuning, etc can vary a lot. That’s why we put some larger and overlapping power levels above. It’s not like all OEM spark plugs are going to start having endless issues right at 375-400whp. Likewise, 2-step colder spark plugs are probably OK even at 400whp. These aren’t exhaustive lists, but a few common BMW spark plugs. Champion are OEM on many newer BMW engines. Bosch and NGK are also common OEM spark plugs for BMW. N54 1-Step & 2-Step Colder Spark Plugs unlike the 95770 washer that deforms, the solid copper crush washer doesn't function by geometrically deforming once.