Just had a Bosal exhaust fitted to my 1995 850 2.5 estate, happy to report it is of good quality construction, fitted perfectly and sounds right i.e it has the usual distinctive 850 tone at low revs but with no untoward resonance or booming.
I am very happy as I agonised over getting an OE item (at 50% more cost) because I have had aftermarket exhausts on previous cars which sounded noiser than the blowing original!