05 mustang GT performance white

First time on here. Need help. Have recently changed my spark plugs to e3.70 and installed SR performance coils. But now when I turn on my car it has a stutter still.
Also another thing I can turn my car on and it idles at 5-600 rpm and I turn on AC n it drops to 2-300 RPMs. Anybody tell me why.
 
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