Regarding part of a previous response to the pink ring discussion, pink ring
doesn't necessarily result due to "porous" electroless copper or small voids.
 I suppose it can but consider this: occurrrence of the dissloution of the
oxide takes place in acid copper only when the current is on.  

Run some tests with and without current.  Put a load of boards in an acid
copper tank for the full plating cycle (e.g. 1 hr.), without current and
there should be little or no pink ring.  Put the boards in an acid copper
tank with any kind of normal plating current density and the dissolution
should occur within the first 5 minutes of plating.

The acids that can cause the oxide dissolution can also be present before
electroless copper, i.e. microetch, pre-dip, catylyst, and/or accelerator (if
one is used).  This suggests that the dissolution is electrolytically
influenced.