I had a friend who is pretty mechanically inclined take a quick look at it and he said it sounds like one of the pulley bearings are going bad.
Just to be on the safe side I'm gonna replace the tensioner with a gates tensioner and the idler pulley with a Dayco idler pulley, because apparently the gates idler pulley doesn't use the stock bolt and washer, but the dayco one does!
As usual, I will update if this solves my issue!
UPDATE: So I ended getting a Gates tensioner and a Gates idler pulley installed. Seems to be going good now! The bearings on the new pulleys are nice and smooth, the 27 year oem ones were quite crunchy xD