Hello Dan,
Try switching the Amsoil back in the engine a few times while also switching the Mobil in between
the Amsoil switches. See if the engine runs rough every time the Amsoil is put into the engine, this should clear up if the engine just does not like the Amsoil or if there was something
else going on.
I really think something else was going on,
I remember a few years back, friend put Amsoil
into his Honda and a couple of days later the battery went dead. Jokingly, he said maybe the Amsoil fluid was negatively charged and drain his battery somehow or another.