Miss at and just off idle

Hi guys, I have a 2000 contour with the 2.5L Duratec engine. I have recently been experiencing an intermittent miss at idle or just off idle. It does not miss at any RPM over 2500. I can duplicate the problem with a stall test (foot on brake, in drive, and apply gas while maintaining foot on brake).

The plugs were fairly recently changed from Motorcraft (original) to Autolite AP764 gapped at .044.

Any ideas as to what the cause could be?

Thanks anyway, I replaced the Autolite spark plugs with Bosch and the problem has gone away.