I replaced the spark plugs and coil boots and one coil pack on my 1999 Grand Am. My car runs much better but when I turn the air conditioning on it runs really rough. What do I need to do next?

Runs rough only at idle but runs good at highway speeds? If so possibly dirty/faulty idle air control valve or dirty throttle plate.

a/c adds load so what about plug wires (that you neglected to change.} Spark breaking down.Air flow like dandyoun said,throttle body,sucking air somewhere,etc.

How about just a plain old fashioned dirty filter?

my car is doing the same thing its a 2001 Pontiac Grand Am se 4 door coupe with a 2.4 liter 4 cylinder. I had this problem once before and it turned out to be the plastic cover that protected my coil packs had cracks in it. it was causing my coil packs to spark and short out against the ground chassis once the plastic cover was replaced problem was taken care of and fixed until 2 years later, now starting with the same problem only milder. I don't know what to do I'm ready to take it to a shop. I'm frustrated!