Probably your canister. The link below is to some technical information that will help you make that determination.
http://www.************/newsletter/2005_N105_Newsletter.pdf
Scroll down about page 3 or so
Other thoughts - throw the canister away. and .... the fuel line at the front of the engine...running from the "hard line" under the mani to the fuel rail will leak intermittently at the clamp to the hard line.
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