I called sportmatech performance and they won't take it back because I already installed it. they said that I might have installed it the wrong way and I didn't adjust the valve correctly. For god sake!!! if you could only see the wall that have been shave off from the lobe it's pathetic. So I took a picture off the head and emailed it to him and he had to comment. But still he wont take it back.What a F**k head. no more business with this guy from me.