I own a 97 A4 Quatro, and have had cel p0455 come on. I followed the obvious path and replaced my gas cap. I am still getting the MIL code being thrown. After i clear the code, it does not come on right away, it usually takes a decent amount of driving (25-50 miles or so). Does anyone have any other directions they could point me in to help fix the problem. Thanks in advance.
Brian

 

P0455 = large leak in the EVAP system check vacuum pipes - hose connections - EVAP purge valve