yes if you piss in a cup it can test you positive for meth/amphetamines, you will have to make sure they send it out to be tested, make sure you tell them you are taking BronkAid or Primatene since you have sinus issues...
If they send it to a lab, even if it tests positive gas chromography will tell the difference between crystal meth and ephedrine use.
If you have the job interview next week, lay off it until then..You don't want a questionable first impression...a very high dosage of ephedrine in your system can make the testing ratios harder to decipher.
Worse case scenario, you can speak to the MRO (medical review officer) explain to him the situation.