I’d check the exhaust system, particularly the silencer if it is still the original Volvo fttng with stainless ends. They are known to suffer from internal corrosion due to lack of oxygen. If it is the silencer thats leaking, don’t waste time or money on getting it repaired, or buying a Volvo replacement as they are too expensive and will only corrode again. Change it for a plastic silencer which will be much cheaper and probably last longer. Force4 chandlery in the UK have them at something under £80 last time I looked.