Is there any way that you could post a picture of this part, and where it is on the engine. I have a 2003 alero 3.4L and I am experiencing he exact same problem. I have changed or inspected everything else you and others have described to no avail.
As this is my wife'* car she is not only insulting my car savy for not having fixed it yet, and growing increasingly irritated that she has no car.
Thank you for chronicling your problem.