So I will close out this thread by telling everyone that more than likely you have to get an Idler Pulley from a MB Dealership. I searched high and low online and everytime I searched for an idler pulley, it showed the smaller ribbed pulley. I took the 90MM pulley off and went to the MB Dealership. As soon as the Parts Guy saw it, he said "Looks like you need an idler pulley." The MB dealership had one in stock. It was a little steep ($84 bucks), but my research time cost more than that. I put the pulley on this evening and am ready for the GTG tomorrow.

Looks like a nice day in Houston/Galveston.

Thanks Everyone!