u/EveningPitiful6164

What do y’all think this could be? A friend said it could be exhaust leak but want to get a second opinion.

My 2003 320ci had a hydraulic tensioner from factory then I bought a mechanical one cause it was the first one I found. After I put it in the same place used the same bolts too. It couldn’t but the new belt on. First u thought I was just ass but then I put the old hydraulic one on and I put the belt on easily. I’m just wondering before I buy the hydraulic one, if I mounted the mechanical one wrong or is it even possible to swap.