The electrical switch is on the intake, not the exhaust, I think, and it most likely is the pressure switch.

Turbo is probably OK -- axial play is along axis -- straght in and out, radial play is side to side.

Funny popping noises and intermittant loss of power sounds like leaking fuel lines to me -- if the suction line from the tank is bad, you pull air in instead of fuel. Check the line from the steel pipe to the injection pump for evidence of fuel or deteriorated rubber under the cloth braid. Eventually you will have serious starting trouble if this is the problem.

The ALDA is the aluminum "can" on top of the IP -- sort of squarish. It will have a white plastic line attached, or should have. The shutoff is on the back of the IP, I think, has a brown with blue stripe plastic line on it.

The ALDA (altitude compesator) adjusts the fuel injected for intake manifold pressure. This means it adds fuel as the pressure goes up, so if the pressure sensing line is bad, you don't get extra fuel to go along with the extra boost from the turbo.

If it feels like the car is going comletely dead intermittantly, I would suspect a leaking fuel line -- plugged tank screen or fuel filter usually consistantly reduces power, not intermittantly.

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!