Apologies in advance for the length of the post; I've tried to be concise but thorough, and this is what I've produced. For about the last six weeks or so, I've had an annoying sound coming from my FiST as I drive, and I'm not sure what to make of it. Any useful suggestions or ideas about what it is and what to do about it would be greatly appreciated. I love my car, but it's hard to convince others of the splendid nature of my beautiful little Race Red FiST when it makes an odd, potentially worrisome, and at the moment inexplicable sound. Context: the car has not quite 6000 miles on it. The only significant modification done is the installation of a drop-in K&N air filter back in March/April or so. The sound did NOT arise until several weeks later. I drive the car primarily in city traffic, around and about town locally, but it has made a few highway trips as well. In addition, I've taken up autocross with the local club this year, and I've done four local events and the Starting Line school. The oil has been changed a couple times, the first at about 700 miles or so. No check engine lights, ever, and I also use, when running about town, a device plugged in to the OBD-II port, called an Automatic Link, which communicates to me about gas mileage, how efficient my driving habits are, etc. It also monitors the engine and thus far has always indicated that no problems have been detected, which I interpret as no fault codes arising, though I don't know how completely the device monitors all the information accessible through that port. In driving about, I've not noticed any decrement in performance or other issues. I now describe the sound as a moderately high-pitched blowing sound, almost a whine, that sounds somewhat like blowing across the top of a partially filled wine bottle. It arises when the throttle is pressed and the engine is under modest to moderate load, at RPMs somewhere between 2K and 3.5K. As the modest strain on the engine is relieved, the sound ceases, and it recurs when the right combination of engine workload and RPM arises. It is somewhat variable in intensity, being easily heard at times, and at other times not as noticeable. It is, however, now nearly always present. It seems to my ear to come from the rear of the engine bay. It is not usually heard when revving the car in neutral. I took the vehicle to the dealer from which I bought the car just over a month ago to have them check it out. The appointment was in the afternoon, and I drove around a fair bit, running errands and the like, before arriving at the service department, already knowing that the sound was less prominent than it had been earlier in the day. After sitting a while, off, a tech and I got in the car for a short drive, and although I could barely discern the sound, the tech could not make it out, and so nothing further was done. Although this might suggest that the sound lessens as the engine warms, I've not been able to confirm by other observations that there is such a pattern to its presence. The character of the noise is not pleasant, and I don't think it is one that auto engineers and designers would want to have emanating from the car--for me, it disrupts the pleasure of listening to the engine as I drive. Of concern is that it seems only a minority of owners are noticing this sound, so calling it "normal" without further explanation as to what it is and why only some of us experience it is less than fulfilling. In addition, one member of the forum who confirms that the sound was present in his vehicle experienced a transmission breakdown on a recent road trip, and is reportedly getting a new gearbox installed. Further details not yet available. Here's a short video demonstrating the sound: If you've read this far, thank you. If you've got helpful suggestions/ideas, a double thanks is due. Ford personnel are trying to address the problem, and I've got another service appointment Monday morning. I love my car--I just want this sound eliminated, so I can go back to driving with a silly grin on my face all the time.