Hi,
I'm a new member, although this is my third Taurus.
Coil would be first thought when you swapped did you also use new plug wires?
Check for oil around base of cyl 1 plug (usually from filling or adding oil) as this will cause arcing at the plug intermittently.
Try unpluggin MAF sensor (plastic tube between air cleaner and and throttle body)- if it improves idle replace sensor or try cleaning it first with MAF sensor cleaner- sometimes works sometimes doesn't.
If MAF is ok try putting a vaccum gauge in line with the fuel pressure regulator on the fuel rail, then start the car. You should get a steadily climbing vaccum reading to about 14-18 in/hg at idle the needle should remain steady no drifting or bouncing.
If drifts check fuel filter first then fuel pump pressure.
if bounces check for vaccum leaks at pcv valve, Intake Air pressure, EGR valve or for dirty IAT sensor tip Qtip-NO SOLVENTS, or Intake air pressure (on manifold) kight compressed air (no more than 25 psi) and/or MAF cleaner (will not damage plastic component)
Good luck!