98 saturn sl stalling at lights, blowing white smoke

hello my name is ken, i have a 1998 saturn i believe its just the sl DOHC. for some time i was having problems with starting it up and keeping it running without having to mash down the gas pedal, it blows whiteish smoke when i do this. now its stalling out when i put it into gears from park, and has trouble starting back up. i have to mash the gas to get it to turn over. also now at stopsigns and lights, when i give it gas to go, it either stutters for a few seconds then kicks in, or it just dies out and stalls. again, its hard to start back up i have to mash the gas down. when i do this the whole car rumbles and blows smoke. it has no problems when im coasting along i can let on/off the gas pedal and it runs fine. now my car is unreliable to drive. my thoughts are, fuel pump/filter, o2 sensors, clogged CAT, Tranny, fuel injectors or a relay or sensor im not sure of. i have replaced my TPS, MAP and air charge temp sensor. i have little money to throw at it. i need some expert advice!