Evap leak near gas tank

[evers310]

My '98 RS makes a loud whistling sound from the rear of the car during hard acceleration. My check engine light is on, I have a scantool and Digimoto, the error code is "gross evap leak" (I'll get the exact error number if anyone wants it). Also, when I firt start the car cold I can hear a surging whistle sound coming from the back of the car. Gas cap has already been replaced. I have done a quick inspection of the evap vacuum lines near the gas tank and they appear to be ok. I know there are some lines on top of the tank but I really hate to have to drop the tank. does anyone know what the cause of this could be? Is it possibly one of the valve controls that is stuck? (cant remember the exact names, they are black plastic pieces that the vacuum lines attach to near the tank) Also, could it have anything to do with the EGR?

TIA

 

[evers310]

I also wanted to mention that even though the fuel cap was replaced it's not an OEM part. Also, I dont know if there is any loss of performance due to this because I just bought the vehicle 2 months ago and it was an existing issue. Any ideas?

 

[evers310]

Ok, for anyone that cares... I plugged the vacuum line from the engine and it still whistles. I guess it's the gas tank itself. I'm thinking that one of the rubber gaskets that seals the vacuum hose inlets on top of the tank are broken. Anyone had this experience before? Any help is appreciated, thanks.