I have one
I have one on my pony and it looks great. it is a little expensive but it is suppose to be real good. For me its hard to tell if it made a huge difference because i also put new pipes in 2 days after i installed the WMS.
If you do order it be prepared to curse a little because the instructions are horrible but i figured it out and I'm no mechanic.
with the new pipes and CAI my track times went down about .25 easy.
And i didnt have to tune it and it runs good.
For the two days i had just the CAI as an upgrade i could hear it a little but i could feel the difference when i went up steep hills around my house a slow speeds. but i didnt get a chance to test it out on the top end.