You will need to replace it with a muffler to reduce the noise and retain the back pressure -- else you risk burnt valves and it will be louder than stock.

Some performance enhancement will ensue, but these days the restriction of the converter isn't what it was originally, there won't be a huge gain.

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!