I am looking at replacing my Z6's on my 08 RT. I noticed that there is a new version of the Z6 called Interact. I went to the Metzeler website, and the way I understand it, the main advantage is that the Interact can be used with another Interact or the standard Z6. This tire costs less, but I cannot see any real difference other than the fact that it appears to be a non-model specific tire, where the standard Z6 with the "K" code must be used on my RT. While I naturally want to save a few dollars, I want to be sure that this tire is as good as its previous version. Maybe Metzeler is saving on the manufacturing process by producing a universal tire, and passing the savings on. Can anyone shed some light on this for me??