1991 Geo Metro Lack of Power

My 1991 Geo Metro LSI Convertible automatic L3 1.0 L will idle for a short time then die. Driveability- it has litlle powr to pull itself along. If I push on the gas it doesn't accellerate as I putter along. Replaced plugs, plug wires, and rotor and cap as well as vacum advance tubing to the distrubutor. No help. Timing is beyond 20 deg BTDC. Apparently the belt slipped one or two teeth so I realigned timing marks on cam shaft pulley and crank shaft pulley. I can adjust timing closer to 6 deg BTDC but engine idles badly, will die and no power. If I adjust the timing the other way it idles up faster, stays running and has a little more power. Where do I go from here to solve this problem?
Thanks