If you remove the black cover over that shift valve and look at the cam on the valve, it does two things. It conrols EGR and it has a cam that directly affects the movement of the bowden cable. In fact, the bowden cable is moved by that cam. The throttle is part of the entire setup, but that cam is what moves the bowden cable. Take yours off and look sometime. If this valve is bad, then you won't get correct pressure on your mityvac at the modulator. It definitely does more than EGR.

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1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup