I just got done designing a new serpentine belt tensioner for the GTM. This solves a few different issues and it all came about while installing an LS7. Any of you who have installed the LS7 know that the FFR belt tensioner bracket does not work with the LS7 intake manifold. The auto tensioner hits the vacuum port on the intake. This tensioner also fixes a few different "problems", like the flex in the FFR bracket causing belt misalignment, the fact that revving the engine causes the auto tensioner to slack the belt, leaving the crank pulley trying to "push" the belt across the waterpump pulley, the extremely close clearance between the tensioner pulley and waterfall, etc, etc.
http://vraptorspeedworks.com/ls-serp...-complete-kit/
You can find it on the "Custom GTM Parts" page at the top of the "Brackets/Mounts/"fixes" section