Everytime I see an "Evap" related code I cringe. I've had to wrestle with a couple, and without a good shops' full diagnostic equipment, I never would have found them. I let the shop find the leak, then I fix it.
So far, this code has been fixed (for me, on other vehicles) by:
-Replacing the Evap canister purge control solenoid (on a Nissan, but we got 'em too.).
-Replacing the Evap canister (had a pinhole leak in it, very tough to find).

Let us know how it goes, it'd be nice to assemble a CEL database (what it is, how to fix) -I used to have one of these in my Subaru days (CELs are very common in modded WRXs, heck, I still keep a scanner under my seat).