So after trying to find the spring loaded serpentine belt tensioner for 3 hours, I finally found out that, like many Mitsubishis, the endeavor doesn't have the common "Spring Loaded" Serp belt tensioner, and instead uses a few bolts to relieve the tension in the serpentine belt so it can be removed. Where the heck are those bolts? One is on the center pulley wheel, that gets loosened first, but I can't seem to find the second one.

 

For anyone else trying to loosen the tension pulley on the serpentine belt, here is the solution. First loosen the tensioner pulley and then find the bolt located beneath the tensioner pulley. It is sort of behind and under, it's orientation is that the bolt is facing upward towards the hood. Loosen this bolt and the tensioner pulley will relieve the tenison allowing you to remove the serpentine belt.