On occasion, there may be a vehicle that will net some gain, but most of the time, the net is zero hp. One issue that they rely on with newer model cars is that the factory airbox cfm intake exceeds the throttle body's cfm. That means that the factory airbox/filter already can supply more air than the engine can gulp.

I don't know what your running for a breather, but I have a 77, 400 grand prix breather. Not that I'm a fan of Fram fliters and I wouldn't use one on my car for oil, I use a fram C-136 filter and don't have a clue as to how tall it stands.