Is the little rubber bump stop still in place on the rear hanger? If not, the muffler may be tapping on the hanger under hard acceleration. I'd check the engine and tranny mounts, too, as if they are bad, the allow the exhaust to shake more than it should.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!