I assumed he was calling the intake a plenum. I found the EVAP leak. It's at the tank. The little plastic nipple that the EVAP line plugs into at the tank broke off. I tried to JB Weld it without dropping the tank but it didn't work. I'm going to drop the tank and fix it. And I replaced all vacuum hose. This truck is from Arizona so all the plastic is very brittle. But at least the rust is almost non existent.