I would pull the intake, and pull the lifters out and spin the engine over ( would be better if you can get a oil pump drive in there, but I don't think you can with a 4th gen?) you want to see if oil is actually getting pumped into the lifter bores. Start by pulling the furthest one back out, see if oil is coming out, then replace it, and remove the next one forward etc.

Couple Ideas:

1) Oil to the lifters is routed through the cam bearings, could you not have gotten the holes lined up, or maybe one walked?

2) Did you use Molycoat or something thick in the break in process that could have clogged the lifters? Oil goes thru the lifters then up the pushrod, so clogged lifters will collaps and no oil gets to the top end.

3) Are you pulling oil pressure from the port near the oil filter or back of the block?

4) What oil pump are you running? Should you have 50 PSI, or could that be a sign on an internal blockage.