Check Engine Light-99 A8 4.2
 

my obd2 scanner reads code P0442
EVAP Emission Contr.Sys.(Small Leak) Leak Detected

Wondering where to start troubleshooting? checked the easiest thing, the gas cap is tight. I erased the code but came back the next day when driving after about 50km. pcv or evap line? any help would be appreciated.
Thanx