piston ring seal or rering

Be sure to check the intake seal. I would pull the intake and look for oil in the runners. Were the heads milled at all? I would not put too much stock in so called pro built either. I have seen a lot of so called professional work that was less then impressive. Sounds like rings never seated, could be anything from over rich during break in, to improper bore finish. If its using a low tension ring package bore finish is pretty important.