I might be a legit evaporative emissions leak. Those are a pain to find. Put your car up on a lift and check all your gas lines to make sure nothing cracked or rusted thru. A pinhole leak usually from rust is what typically causes them and are mostly more of an emissions concern. What was the actual code?
"We live for a good time, not a long time."
RIP Colin McRae
Could check the relay and tubing where the system meets the manifold.
Just behind and under the alternator, the evap vapors (from the third gas line down) go thru an electric switch.
Check the connection and the two vapor pipes are ok.
Vapor then goes to the pressure operated valve (passenger side of the alternator) should have two large vapor tubes, one from the electric valve and one connects to the intake tract.
The small third tube goes to the alloy manifold, make sure it's not blocked/cracked.
You could also take the three way valve off and give it the suck/blow test (nohomo) see it works with pressure change.