I certainly don't hear rumbling. Maybe whistle isn't a good description. Around 3300rpm, just a high pitch sound. I need to drive it a bit more when the weather clears and investigate. In the "Air injection" removal download, it mentions the "sound of air moving through the air valves makes a noticeable whistling sound". I would have thought that went away with the AI removed.
Anyway I am ordering the SS's anyway. I liked the looks on your your bike, ssjones, and the comments on how they sounded.
