First, what are you doing to your car that you will need a heavier duty clutch? If you are turboing, then you will need one. If not, stick with the Exedy replacement clutch.
Second, do not get the MS lightened flywheel. It is only about 2lbs lighter than stock so you would be wasting your money. If you really want to spend the money on a flywheel, get the Fidanza. I have one, and there is no performance loss, your engine will not fall apart, and whatever anyone has told you about it that doesn't have one is most likely not true.
Third, I believe there was a TSB issued on the P5 clutch for chattering. I don't know what the issue is, but at least take your car to your mechanic and ask him to drive it and get his opinion.