Long story short, I made a handful of sets a few years ago, and used them on my bikes. A few others on the forum have them as well. At the time the only options for these plates were billet units, which I believe is still the case. I recently dug up the design files and had another batch made because I needed a set for one of my new bikes.

These block off the air injection port on the valve cover and have a few benefits. It reduces the mess and complexity on top of the engine which will shorten the time it takes for maintenance tasks like plugs, valve checks, coil packs, etc.
They will also reduce weight and look awesome, who doesn't want more carbon on their bike. Finally, if you plan to tune your bike, either on the dyno or street with a wideband, you won't get an accurate reading unless you block off this system as it allow air dilution into the exhaust. Obviously these are to be installed by a savvy mechanic and are for offroad use only. $50/set and I will ship flat rate anywhere in the US. outside of the US we will need to determine real shipping cost. Act now if you're ever going to want them, once they are gone it might take me another 10 years to make another batch.