What he said. All the CVO ElectraGlides, going back to the 2004 SEEG, have come with a modified stock plastic airbox instead of a true open SE type air cleaner. While the modified CVO airbox probably does flow better than the standard airbox, it will definitely restrict flow when compared to one of the open varieties on the market. The big question is, do you really need the extra flow or are you considering the high flow air cleaner just because everyone says you should? Open filters flow better, but they can have downsides as well, such as the oil dripping or misting Boatman mentioned and the increased noise level.
Be aware, if you decide to use the SE kit (I wouldn't) or one of the aftermarket versions, that you will need to do some modifications if you want to use the stock cover. You'll find several threads on the site that discuss covers falling off because they broke off the center mounting nut in the end of the filter. You will need to provide better support for the cover, or use a different cover that fits properly to the end of the filter.
Jerry