Question for the gearheads here, I was driving my Miata today, and everything was running fine, when it acted as if it was missing, but would still maintain highway speed, but at lower speeds like traffic stop/go it would just droop and stall out. I pulled over and it would barely idle, and then die again. I could give it throttle and keep it running, though it is running very rough. I limped home and I switched out the plugs wires and spark plugs. Still nothing, and if I don't keep giving it throttle it will die, but always restart, with a little difficulty.

Any ideas? What should I check, and in what order?