Try prying GENTLY along the Clip Edges with a Wide Blade Screw Driver and avoid allowing the sharp edges of the Blade to puncture into the ordinarily tough Black Plastic Canister Body.
I found it necessary to remove the Transmission Cross-member for the R&R of the 4L60E Transmission of my 2002 TB back in 2014, but the Charcoal Canister was in the way. I used this very same slow, deliberate method to pry and pop the Canister Out of its Mount and later used my feet to re-insert it with considerable necessary pressure to get it to go back in place. Use a Bright Flashlight to ensure how everything is oriented under there before you begin. If you have any other Questions regarding how things are situated... Take some Digital Images of the areas in question and Post them up back here in your next reply.
Avoid being too aggresive and risk damaging the Canister Piping Connections.IIRC... It was unnecessary to undo the lines to it in my case for additional Mount Bolt Clearance. Before you actually perform this task, please inquire of other Members for some alternative EVAP solutions that might diagnose a Different Problem that may make doing this laborious task unnecessary. If the R&R is an absolute requirement and you cannot get it to budge... Professional Removal and Installation with a New GM OEM Canister may prove necessary with the Labor Cost being almost as high as the Brand New Charcoal Canister will be.