Idle control valve hoses, it's under the air filter housing. Chances are they are rock hard and leaking, so you have air (and dirt) entering the intake that is not being measured by the air flow meter. This results in a lean condition beyond the ability of the feedback system to adjust, so it runs rough and stalls under load.

The cure is new hoses (one is a real PITA to install), and to check for any other leaking vacuum lines.

You should also check the O2 sensor for proper operation, if it's bad, the mixture won't be right.

Check to make sure it's not running way rich, too (black plugs). This is, alas, a sign of a dead fuel distributor ($$$$$$).

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!