Chevy Aveo Engine problem

I hired a mechanic to replace the timing belt on a 2005 Chevy Aveo. As he was testing it, the timing belt slipped and caused damage to the valves. A machine shop repaired the valve damage. After putting together the engine the car started making a rattling noise, and the car wouldn’t idle properly. When we raise the RPMs the rattling noise goes away and the engine seems to work fine. We identified the rattle noise coming from the PVC valve area and we changed it. We performed idle relearn. We checked all the hoses for leak, but still no luck. We are getting an error code P2279 air intake leak. The mechanic at this point told me that he is stumped and doesn’t know what to do. Any suggestions would be appreciated. Thanks.