Diesel engines don't make that much noise at any power output short of full -- they sound pretty much the same without the muffler as with at idle. Not at all like a gas engine. You will only get more sound at full power.

And the mufflers are flowthroug, anyway... even on my 72 280 SE.

Peter

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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!