We wanted to go through and add some clarity on this. First of all, let us be straight. An atmospheric BOV in and of itself does not impact the power output, however there are a few things that we look at long term here. It was worded poorly on our part, which is why we want to clear it up. #1, while they seem simple to install, they often times are not and we have had numerous instances where they created issues because of improper install. This can of course be said with just about anything, but the BOV is in integral part of the logic in the ECM. There is indeed a reasoning for this, and going pure mechanical is taking a step backwards in technology. If you are chasing sound, that's perfectly fine, but it's not something we recommend as we take it upon ourselves to only recommend products that add to the performance of these cars.
Now, in addition to the possibility of improper install, you do have to take into account the fact that to install this, would require the introduction of metal charge pipes. This is also a technological step backwards. With the constraints of the engine bay, and the fact that there is already a great deal of heat being generated in a tight space, the hard piping associated with an atmospheric BOV is the real root cause of degraded performance.
So, in summary. No, it was phrased incorrectly on our part, an atmospheric BOV does not inhibit power or performance. BUT, it adds nothing, and the other aspects needed to install one makes us feel that it is a step backwards in performance, and technology. Which these two items are what makes the EcoBoost platforms so appealing in the first place, so this is the core to why we do not recommend them.