No, it cannot be adjusted. The modulator adjustment affects whether shifts are hard or soft, the Bowden cable adjusts the throttle points at which shifts occur. Adjusting this will somewhat affect shift harshness too. Engine torque close in both gears being shifted = smoothest. Also, vacuum 'pressure' will vary with engine speed and throttle opening, so shift points will also affect the vacuum the modulator sees.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7