I recently replaced my serpentine belt tensioner. The replacement was an aftermarket version from Febi (made in Germany). I suspect this is the OEM manufacturer for Volvo, but I don't know. Here are my observations on this new part:
The old style has a hex bolt in the middle of the tensioner roller. Due to limited clearance, in order to relieve the belt tension, I put the box (ring) end of a 14MM combination wrench on the hex bolt, and looped the box end of a large wrench over the open-end side of the 14MM, to provide extra leverage. This was a bit cumbersome, especially when re-installing the belt, but it worked.

The new style has a Torx cutout in the casting, just behind the tensioner roller, requiring a T60 torx socket. This was quite a problem. T60 torx sockets are typically 1/2 inch drive. Even attaching the torx socket to a simple breaker bar, there is not enough clearance. I went out and purchased a serpentine belt tool, which includes a thin flat bar, with a half inch square bar on it for the socket. Even this was too long. I had to cut off 3/8" of that half inch square bar before I had enough clearance. Once this was done, the serpentine belt tool ($15) made it a breeze to remove and replace the belt, because of all the leverage it provides.

Although the bearing in the old tensioner was rougher and looser than the new one, the knocking noise that I was hearing through a mechanic's stethoscope persists, because the bearing is a loose fit on the shaft it rests on, allowing it to move on the shaft. So I guess the knocking noise from the bearing is "normal". (This particular knock is definitely from the serpentine belt tensioner, not somewhere else. You can only hear it with the stethoscope.)