The stalling problem is a typical TCC failure. It is a small solenoid in the transmission, only costs 25 bucks but 150 to have installed. A transmission shop needs to install it, it is a bear to try on your own with a 90 model. To be sure, unplug the 4 prong connector at top of the tranny, on right side. If you habe a v-6 motor it would be under the air box assembly. Many if you unplug this and the stalling stops you have have it fixed or leave it unhooked. Will only cost you a little gas mileage. We unplugged ours at 155K, still going at 240K, with a different owner.
The other problem is hard to say....not enough to go on. But be sure the car is tuned well, air ducts to engine are not split open, clean the IAC control to be sure it is working OK, and watch for any check engine lights. Common for an engien that old to have a weak coil, might be mis firing on one cylinder but just guessing.