Oil pump pickup is damaged or loose, I'd bet, so that when the oil rolls back under acceleration, the pump sucks air instead of oil.

This may just be a loose bolt, could be a fractured pipe.

I would DEFINITELY drop the pan and check this out -- oil supply failures will cost you an engine eventually.

Peter

__________________
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!