hey rc, when i had that set up runing i had a similar problem, it definatley felt to me like boost pressure was overcoming fuel pressure. i had a holley blue and the reg bypassed under boost. I tryed all sorts of ways to up the fuel pressure, i tryed streaching the spring in the releaf valve on the fuel pump, but i ended up limiting the boost to under 10 and there was never a problem.
i think to try colder plugs would be well worth a try, even just one heat range. That wouldnt cost a heap of money