I'd also get your DNA tested for the MTHFR mutation.

Errors in methylation, as I quoted to you last week, and Marlene
suggested just recently, may explain your intolerance to Niacin.
(You were not using Niacin BTW, but non flush version called
inositol hexanicotinate). The latter retains some vitamin actions, but is not Niacin and should not cause flushing at all.

This post:
http://neurotalk.psychcentral.com/post1059073-12.html

COMT is a methyl transferase and a genetic mutation in this enzyme involves methylation failures.

If you google, "methylation errors", or "under methylation", or the Pfeiffer Institute as qualifier you will find more.

I would also think getting a heavy metals screening might be useful when you get your testing done at the doctors.