I have an 84 300D Calif emissions. Got to wondering just how much boost I was getting so I put a gauge on it and went for a drive. Barely got anything, only 2 to 3 psi. I was originally between the overboost protection device and the ALDA. Thought it might be the overboost device so I went to the hose off the back of the intake manifold and got the same numbers. Undid the banjo bolt and made sure it was clean as well as the hose. No change. I then undid and removed the U-shaped tube that feeds the inlet of the turbocharger. Very audible turbine whine but only a very slight increase in pressure, not more than 1 psi and probably less.

This slight increase seems to indicate its not a wastegate issue. I can't find a leak in the intake or exhaust manifolds.

Any ideas? The manual says boost should be about 0.75 bar or around 11 psi. Bearing drag? (I recently switched to Delvac 1 but performance has been consistent before and after the change except for better gas mileage) General crap?