Volvo brought their Porsche-designed in-line 6 into the US market in 1992. Like everything else, it took them a couple of years to completely debug it. I am told (but have no direct experience) that the 1992 and 1993 versions have timing belts that wear more quickly than desired. As a result, the owner has to be very diligent about changing the timing belt since this is an interference engine. I also believe that Volvo had a TSB on a tensioner change to one or both model years to try to fix the problem. In any event, I am also told that they finally succeeded during model year 1996 and the belt is good for a lot of miles. Steve Seekins would know much more about this.
This is by all accounts a great engine, even for the earliest model years, and the only requirement for the owner of the older engines is to carefully maintain the belt.