I don't know of any specific issues with the 1991 models. They came in two colors, one is called Onyx and is all black and one is like mine with black frame, white plastics and purple tank and seat.
things to look for IMO, tires, even if good they are probably old and hard. Chain and sprockets. Check for oil seeping around engine and base and if the bike is low miles it has sat a long time so a good carb cleaning and good look inside the fuel tank for rust is in order.
Good luck, hope you get it and post some pics.