how many miles does ur jetta have?
there is a warranty that is called emissions warranty dealers do not talk about. its 7years or 70k miles
there also could be a warranty extension that applies to your car
call and ask a dealer VW , wait call two dealers in your area they will ask for your vin # its on your registration and on your dash left right corner if your the driver, look from outside by windshield. could save you sum$$$$ if its covered under warranty they need to refund your diagnosis charges. if its the oxygen sensor your diag will say bank 1 or bank 2 this is 1- front ox sensor and 2- rear sensor. vacuum will be evap leak (small or large) could just be a hose or fuel cap actually could be many things. a dealer diagnosis will tell you exactly what is bad and needs replaced.
vw service advisor 2+ years