I found some postings are missing too.
The Calif 84 and all 85 300D/SD models have an Air Circulation Valve which is built into the outlet of the turbo. That valve is controlled by a computer. The computer takes input from several sensors and decides when to activate or deactivate the smog devices. These cars have an overvoltage relay to protect the computer. I believe that the air is circulating via internal channel between the fresh air output (toward the intake manifold) and fresh air input (at the air filter side) of the turbo causing low pressure in the intake manifold, therefore, no turbo boot. The computer controls the valve via a vacuum line.
As I stated before, I just start learning things about turbocharger. Please read my statements with an open mind and ready to make corrections if necessary.
The answer is yes to your question about "brought back to prior year" but I have never tried it on any cars.
Los Angeles, Calif.
[Edited by be459 on 05-25-2001 at 01:36 AM]