So here's the update:
I did the same thing as you
beerguy, mounted the base plate on the outside but by accident.
It had the 1/8" gap all the way around but it still had the whistle. So I mounted it the correct way and sealed the corners with black adhesive silicon sealant. I figured, maybe the whistle was coming from the gaps. However, it didn't work.... actually the whistle isn't as constant anymore. Now it's only during certain RPM's and Transmission Shifting. So I guess it did improve but not completely gone. I also messed with the placement of the filter by moving it out a little... in hopes to maybe tune sometime.
Anyway, I'm done messing with it (for now).
As for the noise level, this thing is loud. Like I said, my first review was a little premature. I was driving on the freeway yesterday and during acceleration (2500-3500 rpm) this thing roars. I do like the tone though... I find myself itching to slam on the gas but then I look at my average MPG and the thought of $3.60 a gallon stops me.
