I have been chasing a EVAP leak on my wife's 2003 IS300 for almost a year now. It started out as a P0456 (very small EVAP leak). After doing some investigation (testing solenoids under the hood and on the charcoal canister), the code promoted itself to a P0442 (small EVAP leak), but I was getting P0456 at the same time. I replaced all EVAP related rubber hoses and vacuum lines under the hood with ones from Toyota. Still no improvement. I built a small DIY smoke test machine and traced it down what I thought was a leak in the charcoal canister. I took it to a trusted shop and they confirmed that it was a leaking charcoal canister. I ordered a new Toyota charcoal canister assembly, installed it, and reset the codes. A few weeks later the P0456 code comes back. I took it back to the same shop today and they can't find another leak after testing it twice (smoke and timed pressure test). I'm all out of ideas after checking everything in the Diagnostic Manual. Does anyone else have any ideas for things to look for on this one?
'95 Miata w/ VVT Swap -- Track Car
'03 IS300 -- Wife's car/daily
'14 Ecoboost F150 -- B/c something needed boost.