I, too, have hit the "wall" with my FCR's and kit pods. There is a point where I cannot make more RPMs, at high travel speed, and I know the RPMs are available in lower gears, from the rev limiter engagement. Could it be that we are so aerodynamically "effecient" that there is no way to press that envelope further, without some valances or displacement? The intake restriction of the standard airfilters may be showing itsself, at that point.
I have direct frontal air into the pods and don't have any lateral wind pressure changes noticibly affecting engine output. I get steady throttle RPM hunting with wind changes, but I attribute it to the venting.
edit to add: jetting is a bit fat as well, in my case, could be the last few hundred heavy loaded RPM that needs a leaner main.