An "inconclusive" result means that your reactions to relevant questions were about as strong as your reactions to the so-called "control" questions. The key to passing is to show stronger reactions to the "control" questions than to the relevant questions. Polygraph "testing" has no scientific basis, and the erroneous results do not mean that there is anything wrong with you. It is polygraphy that is flawed. For more on polygraph procedure, and how to reduce the risk of a false positive on your upcoming polygraph examination, see Chapters 3 & 4 of The Lie Behind the Lie Detector.

To address your other question, yes, agencies sometimes do play fast and loose with polygraph results. For example, Roy Ortiz, the head of the LAPD's polygraph unit, was credibly accused of altering polygraph results. This scandal was successfully swept under the rug by the LAPD.

Note also that Ed Gelb, who operates Intercept Inc. and has a contract to provide polygraph services to the Long Beach Police Department, is fraudulently passing himself off as a Ph.D. in marketing his firm's services. However, the American Polygraph Association doesn't consider this to be an ethics violation.