my 97 caravan had the same evap code, I checked all the lines and hoses,changed the gas cap, I don't have a smoke machine,i did not see any cracks in the lines and hoses...had this problem for the past year or so...seems to come up during the colder weather...it just happens that my 3.3 fuel rail leaked and I had to replace it..with that in mind, the pcv hose runs in the back valve cover and it was hard as a rock and brittle to the touch...I changed the hose out with a new pcv and guess what?...all GONE...this was my fix....