1. I naturally breath through my mouth. Could whether you breath through your nose vs. your mouth affect your results??
2. I took a poly for USSS a couple years ago. This was before I was diagnosed as a type 2 diabetic. If for some reason my blood pressure was high that day (due to the unknown illness at the time) could that have produced a false positive???
While both of the factors you mention might well affect the tracings of the polygraph instrument, it seems unlikely that they would do so in a way that would make a false positive outcome more likely. To do so, they would have to differentially affect reactions to relevant vs. "control" questions.
There is little point in trying to guess why an invalid test produced inaccurate results. Polygraph screening has no scientific basis. Your false positive outcome didn't happen because there's something wrong with you. It happened because there's something wrong with polygraphy.