Kinda of confused on what I can and cant do with valve springs. First, Does Itr's have dual valve springs?...I see people stating that you can buy 8 Itr intake springs and install that on the intake side of a gsr, move the 8 gsr intake springs to the exhaust side, and buy 16 portflow inner valve springs to and drop those in too so u will get dual valve springs.... Is this true?... Or do I have to buy 16 Itr Outer w/ 16 portflow inner valve springs? Thanks for the info