Sounds like the car needs some refrigerant added. As a 93, it could be either R12 or R134. You can tell by the fittings. If they look like tire valves, R12, if they are bigger, without threads on the outside, they are R134. If it is R134, you can try adding a can yourself. If the car has a sight glass, just add R134 until the bubbles disappear. If it is R12, you need a shop to top it off, since R12 can only be sold to a licensed tech.
Exotexs-I have to disagree. If a R134 system is properly designed and operating properly, it is as cold as R12. In my 94 XJS, on a 95 degree day, I get 0 degree F air our of my vents. Last week, on a 91 degree day, my glasses iced (not steamed) up when I left the car.
The problem occurs when a system is converted from R12, Depending on the car, you may need a different expansion valve, orifice tube or H valve. Most shops don't do a complete conversion because of the difficulty (the aluminum fittings often corrode and strip out) or because they can get adequate (not optimum) results without doing it.