1997 Pontiac Sunfire SE dying at stops.

I wrote earlier about my 97 Pontiac sunfire. It is an automatic with a 2.4 liter twin cam engine. The problem of it dying at stops is still happening but has gotten worse and now dies completely randomly when starting to slow down, but still restarts but with much more difficulty, and will sometimes just crank even when parked and trying to start. When it does start the engine will shake almost violently and sometimes die although this is not alway's the case. When it does run the idle is very rough but only in between1200 and 1500 RPM's and when I put pressure on the gas pedal it will sometimes get to that RPM usage and then will die start to bog down. I have had the crank sensor, fuel filter, fuel pump, air filter, oil filter, and spark plugs all replaced. I have also cleaned out the throttle bore and air intake system. I still don't think it's a weak ignition spark, and if it is the Idle Control Motor how can I adjust the RPM's, and if I can't and need it to be replaced how much will it usually cost. Could it have anything to do with the crankshaft? There is no check enging light on so the problem wont show up on a diagnostic scan.I hope you can help me out and help me to fix this problem.

No it never misfires on acceleration. So what could be the problems with the coil housings and how much would they cost to replace. Thnx for the info so far. I don't mind paying a little money for repairs butI want to know that they will fix the problem.