Just wanted to give this thread another thumbs up. I have a 2006 GMC Sierra Crew Cab Z71 and was getting codes P0449 and P0455. Replace my canister with ACDELCO 2142149 from Rock Auto (less than $20), along with some rubber heater hose and clips (less than $5). Installation was easy and the check engine light turned off the next day.
Thanks for the great info.