I use the 5 GPI weight tubes in my GT's all the time. There are a couple of things to make sure of a proper installation. If properly installed they WILL NOT buzzzzzzzz. If you DON'T install them correctly, then yes, they'll buzz on ya.
1. Make sure you have the right diameter tube. Different brand of arrows require different diameter tubes.
2. Cut em about 0.020 or 0.025" long. That way when you press the nock in place it will compress the tube just a bit and prevent it from rattling.
3. Glue in your nocks with Goat Tuff. If you need to replace a nock, run an 8-32 tap into it, heat the tap just a bit and the glue will soften to allow the old nock to come out and it will not damage the shaft if you are careful.