Engine light came on again. Evaporation system code. Again. What can be the problem

What is your question?

Engine light came on. Evaporation system code. Mechanic did a fume test. Charcoal canister supposedly was cracked. I ordered the original part. We changed it. After 2 days. Same thing happened. and i smelled gas. Im not sure it was mine,i was on the highway when this happened. I mean. WhenThe engine light came on. But i think it was. Thank you

What makes this problem better or worse?

I dont think the two are related,but my rpm after a full stop or slowing down its unstable,like im trying to catch speed but abruptly the rpm drops then i have to push gas very gently,and after i pass 40 mph doesnt shake,jump or have any issues. But between those 5-25mph

How long has your 2006 Toyota Camry had this problem?

Just recently bought the car,so ever since. But prior to that i wouldnt know,What i know os that the guy changed the tank cap right before i bought it.