My local Mopar machine shop (that has built and raced Mopar engines for many years) has mentioned to me that it's not too unusual to have some fuel distribution variance, in particular, to be leaner on #8. Something about it being an end cylinder in combination with the way the firing order is designed.
And maybe this would be worse at idle as well???
(this according to my memory of a conversation months ago, so... you know.) :)
