hard to start and runs slow

My mitsubishi spacewagon 1999 model stalls and does not do slow running. Most times while doing slow running, it goes off when the automatic gear is engaged. what do i do? The problem started when the engine just began to go off when doing slow running. After two days it became hard to start it at all. Mechanic suspected Fuel pump, fuel filter, injector head and air flow meter. All these were replaced yet the vehicle gives hard start and the slow still not good.