1998 Chevy. Lumina Help Please!!

Hey all, I've turned to you all in the past and I return once again!
I have a 1998 Lumina 3.1, I reccently have had a heck of a time with this car. When idleing its fine, but, put it in drive and its like being in a paint mixer. I was told to replace the fuel filter, which I did and it ran fine for 3 days... then I was told to take it to AutoZone to get a code which I did I was getting Multiple missfires, with suggestions from here and the AutoZone guy, I replaced one of the ignition coils, he showed my hubby how to test it with a OEM(SP?) meter, well it ran like a champ for 3 days, so we went and got the next ignition coil. This didn't effect it at all!! Its still jerking and stuttering like all holy heck. I am contemplating this deeply..
What next do I go buy the 3rd and final coil? and pray that its money not wasted? or what?
The car has 88,000 and is a champ when running correctly but, It feel so wrong to be driving it, but its all we have. I am all for suggestions - if there is a way to make it last until income tax I can sink a couple of dollars into it... btu I need help! I am handy, I replaced the alternator, starter, the battery, the plugs, the wires, So any suggestions welcome!

Thank you in advance!
L

maybe its ignition module related. The 98's are obd2, have that mechanic pull you a code, it should be able to tell you what cylinder is misfiring, or if its random misfires. I dont know. It is odd that it idles fine. Does heat have any effect on it? Does it act the same way cold as to warmed up? Good luck

Agree with Blake. If its the same cylinders misfiring, and changing the coils didn't work, go for the ICM...or the wires/plugs. If its a random misfire, target just the ICM. Those things are heat-sensitive when they get old and start to go bad, so usually when the car is warm they'll act up most in my experience.