My 300sdl transmission vacuum modulator leaks when the tyranny is at operating temperature. Also the transmission will flare when anything but moderate acceleration is used. .....

Would a bad modulator cause flaring? I am thinking new o rings would not be sufficient if the modulator is also bad... shouldn't a bad modulator cause hard shifts instead if flares though ? ??

Well, I guess I found my answer:

Transmission Slips In All Gears
Incorrect modulating pressure. Modulating pressure control
valve or pressure relief valve is dirty or sticking. Vacuum line to
transmission vacuum capsule clogged or leaking. Working pressure
control valve dirty or sticking. Low working pressure. Defective
primary pump.