Wastegate may be worn, so it doesn't seal properly when closed. Or the turbo is going, and wont' come up to speed. Note that you must have full load to get full boost, and that means driving it with a boost gauge installed, you cannot measure it properly with the car stationary unless you have a proper dyno (not one of those silly little "10 second" ones).

The other other adjustment is to change the spring on the wastegate controller -- it is probably weak by now, and not allowing enough boost.

11 psi is within factory spec, and is the usual pressure in a good system.

Do not exceed 13.1 psi unless you don't care if the engine blows in a year or so.

Most preformance complaints can be "fixed" by increasing the ALDA responce a bit, they lose effectiveness with age.


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!