Having a long running issue with our 2001 Corolla (130k) and codes P0440/P0442. Thought I might get some help here.

History:

9/30/2014 Check engine light on. CODE P0442 Replaced gas cap, cleared and re-tested clear

Light came back on after a few days, we were told that it was safe to drive, but we should get an evap test done sometime.

1/27/15 Evap test done, no leak found. CEL reset

Summer 2015 Bought an ODBII scan tool. Regularly checked and cleared P0440 and P0442

During 2015 taken in a few times for oil and filter changes, no work done on evap issue, but codes cleared and noted

2/5/16 Evap control canister replaced 120k service

Codes came back on 2 days later (before attempting smog)

2/13/16 Vacuum valve purchased, and replaced Smog passed before the car was returned to me

7/1/16 vacuum switching valve assembly replaced

As of this week: Codes back on.

At this point I'm really uncertain that the mechanic has any idea what they're doing (it's been the same mechanic for all of the above, except the evap test). Any suggestions from those of you who have had similar issues and gotten them resolved?

Thanks.