My impressions of the Rune with the k&N adapter:
Sound- sounds louder, but not significantly more.
The people i normally ride with asked if i did something to the exhaust, they noticed it was louder.
During a hard exceleration, i can hear the air being "sucked" into the engine.
Power-Here is MY impressions, and some may not agree with me:
The power band has shifted farther up the RPM range. Since i don't have a tach, i cant say where exactly it is, but i definitely notice more response at higher speeds than before. riding steady and then accellerating with a Hard throttle at 60, 70 and 80 is more pronounced than without this mod. The low speed power seems to have lost a little response, but nothing significant. In fact, I don't have that "really sensitive" throttle that lurches forward when you hit a bump or hole, it seems to be more stable. Still has the quick excelleration at low speeds, just not the the overly sensitive throttle.
Feel- It bike feels different. There is a different vibration to the motor than before. Not rough, but you can "FEEL" the bike run, where before it was a smoother, more fluid feeling.
Overall, i would have to say it is a positve Mod, and i will keep it on the bike.