i am changing the timing belts on my 308gtsi i know the owner before me change the 2 cam timing sprokets cause thay spon. goin from plastic to metal my question is do i change the other 2 form plastic to metal or aluminim or live it alone . i have a feeling that if i do NOT change them i am taking a big chance. i, need som advice on this and where can i get them at a good price. thanks.