There's an adjusting nut on the valve too, under a dome shaped cap towards the front of the car. You can adjust the vacuum range with that. I wouldn't go crazy with jacking up the modulator on the tranny, mine blew the tranny not long after doing all the same stuff you are going through....

__________________
So far...'76 240 D (sold)
'84 300SD (sold)
'85 300D (sold)
'83 300SD (p.o.s. waiting on tranny swap)
'82 300SD (could be the keeper)