Taking the slack out of the Bowden cable will make the trans shift later, but won't help the soft shifts. Try turning the modulator valve on the driver's side of the transmission clockwise. A search will tell you more about the modulator valve than you ever wanted to know . If you're having trouble finding it, it's next to the neutral safety switch and has a vacuum line (should be black) going to it.

__________________
1982 300D, black w/ palomino leather, 203K
2001 E320, champagne, 105K (Mom's)
1999 Dodge Dakota, squeaky & battered, 142K