whinin

So this thing was running well (between 11.0-11.8 afr at all rev ranges) before I tore it apart. I put lower comp pistons and had a valve job done (along with others but these are the only things I think would change the tune). How much will this change the tune? I ask because I will be breaking the motor in (haven't started it up yet) these next few weeks, and want to be sure it's not going to go lean on me when I take it up to 6k to seat the rings. Thanks for any help!