How 's the fuel pressure?
BTW: didn't you change out the ICV?
I'm thinking tank ventilation is related to the purge system but I wonder how the ECU determines there to be a problem with it. I don't know of any sensors on that system so I think your ECU is just guessing. Could still be broken FPR. After all, it is part of the recirculation of fuel. If the FPR is stuck closed fuel pressure should be higher than normal.