Undesirable candidate,

Your concerns are valid.  Unless you confessed or admitted wrongdoing, your letter has stated that "you were not within acceptable parameters."    The FBI has very carefully worded this letter so that they could not be challenged for accusing you of "deception." While everyone and their brother will assume you were deceptive (an inference that the FBI does not do anything to clarify or reject), you have not been judged in writting that you are untrustworthy.

I have had military clearances and currently Dept of Justice clearances which I was concerned about.  I was eventually offered a third polygraph and cleared my name (after many well thought letters of appeal and political chess playing).

It is personal to you and I but the FBI, CIA, NAS, and many government agencies consider it to be very acceptable to have false positives.  They are very aware of its shortcomings but it comes down to money issues.  They have a surplus of qualified candidates and if you read carefully on their webpages, they specifically state that the background check will not be done unless the polygraph is successfully passed.  This is a big catch-22 since you cannot demand they provide actual evidence of wrongdoing concerning being "unacceptalbe."  They save money and you are guilty without evidence that any court in the nation would demand.

If the polygraph were to become excessively expensive to perform, it would be eliminated tomorrow.  If the voice analysis methods become cheaper and easier to administer, regardless of any validity arguments, it will surpass and replace the polygraph.

Delay any letters to Congressmen and other officials outside the chain of FBI command until you exhaust your appeals.

Good Luck,

Fair Chance