Sounds like quite a mess---Nobody can say what it is you
have without actually looking at it. I have two thoughts, though.
The recommended burnout temp. is 1350f., by the way. I've never done
the silver wire thing you describe, but the thinner the silver, and
the hotter the flask (and thus the SS wires) at the time you cast,
the more instantaneously they will dissolve in molten gold. And make
sure you soak it good, so the core is the same temp. More
importantly, though-- If you have cracks/seams where wax meets wax,
or if you have small holes and the like, such as if you drilled the
wax with pilot holes, then you have tiny pieces or flakes or rods of
investment, after the wax burns away. Investment WILL go inside of
incomplete (un-fused) seams of waxwork. Then, when the heavy mass of
metal (very much especially platinum), comes roaring through, it
breaks off those tiny pieces, and becomes just the sort of porosity
you describe: Giant holes with crud inside of them, usually impossible to fix.....