As that thread,
https://www.volvoforums.org.uk/showthread.php?t=290215
if you're already spending money on fuel it'll be worthwhile. And it'll be worth your while to investigate how to do it well.
if you're going to deal in somebody else's lash-up, best you leave well alone. Done badly the results will at best be variable. But that's like anything else not done well, not LPG's fault. There's many poor installs out there,a dn LPG gets a poor rap for it.
If like me, you minded to put your own kit on, AND do it well, you'll definitely never regret it. If you're looking for a pro, look hard, and be sure you've got the right one.