I was pleasently surprised when a whole series of tests showed all internal organs were unremarkable and no significant accumulation of lead
It would be helpful if you could say what specific tests you under took.
Did you have any Neuropsychological or Neurophysiological testing carried out?
What particular Blood tests did you have?
Did you have a Fat Biopsy?
It is all very well saying that you had tests carried out but if they were not the correct ones then the results are meaningless.
It is a bit like having a Blood test for Alcohol.
Sure, they will not find any traces of lead or other chemicals as they are not looking for them in those tests, they have to be specifically for the Hydrocarbons, CO, TCP, other SVOC's & VOC's.