P0455 Check Engine Light
 

Ok, I understand this has been asked a million times on here as I have done some searching. Trying to narrow down if it is a bad gas cap which I am hoping it is. Mine is comming back as large leak, if it were a bad gas cap would it be comming back as small leak? And if thats the case since mine is large leak detected could I rule out bad gas cap and suspect it's the other probable symptoms? Also, is there a specific gas cap needed for the 04 GT MT? Or can I get a aftermarket one? Any help would be great.

Large evap leak can still be the gas cap.