Dan, it could definately be the valve seals or the turbo seals. I've seen friends with brand new turbos that needed replaced because the seals were bad, though that is rare. The valve seals would typically smoke under idle after idling for a while, and at start-up. You should notice milky coolant if it's the head gasket.
Or it could be the oil rings and this is what I'm leaning towards. You can have perfect compression numbers and still get tons of oil past the oil rings, meaning the other compression rings are fine. I know this first hand, my Talon smoked BAD under boost and when decelerating after hard throttle but was perfectly fine at idle and cruise. I first replaced the turbo but ened up having to redo the bottom end. Don't rule out the turbo seals though.
What pistons/rings were installed in your new block? What did the shop recommend for break-in? If those are Total Seal rings then that shop doesn't know what they're doing and you must replace them. Total Seal rings will not seat with the metal of our shortblocks. It has to do with the high nickel content of our blocks not mating well with whatever Total Seal rings are made of.