please help.. miata problem

Hi all. I have a 1990 miata and ever since i got it its been having problem after problem. Ive done a full tune up I believe. Here's a list of things i've done change catalytic converter spark plugs all fluids spark plug wires fuel filter CAS coil pack

So my beauty drives very good SOMETIMES with no problems at all, but lately it's been stalling at stops and will have trouble turning back on when stalling. When I first turn the car on it'll stall till its warmed up a bit. Say I'm going to the store, turn the car off obviously, when I get back she will be difficult to turn back on. When it does turn back on it'll stall if i don't give it gas. I have checked for fluid leaks and vacuum leaks but nothing. I'm not sure what the problem would be. I've checked for OBD1 but that never seems to work. What do you guys think? thanks all for the help.