I realize this is an old yet ongoing thread. I thought I'd list my experience in case anyone runs across this.
Our 2005 Tahoe with roughly 160K (at the time) started having fuel filling issues. if you tried to lock the handle it would either shut off, or spill gas everywehere. We would sometimes get the "tighten gas cap" message as well. But sometimes it would go days and days without displaying that message. We also never once had a code. Just slow fill and occasional tighten gas cap message. So I replaced the solenoid...didn't work. Started researching, watching YT videos etc and found many people talking about vent lines and them becoming clogged with charcoal pellets which keeps the tank from releasing pressure as you fill. So I disconnected the line with the white clip going from the tank to the evap canister and sure enough, tons of pellets fell all over the floor. That's actually the only line I could get free, but I knew right away what the issue was. I tried hooking a shop vac to that line to suck out while someone up top opened and closed the gas cap to allow the fuel tank to expand and contract. This removed some pellets, but issue was still there. So, I was prepared to drop the tank, but then I found a guy in the comments of a YT video that said he didn't drop his tank at all. He simply disconnected the lines to the evap canister and stuck the tip of his leaf blower into the gas fill tube, and turned it on. He said pellets flew out all over the ground and issue was resolved. Reading that I decided to take a funnel, cut the end off to open the hole up a bit bigger (more velocity) and stuck it into the gas fill tube. Took my shop vac on exhaust side (cleaned it out of course) and blew into the funnel. Pellets came out everywhere. Went to get gas, filled up faster than it ever has. We still get an occasional "tighten gas cap" message, but the truck has been driven mayb an hour since I did all of this. Not sure if that'll go away after driving it more, like a code does. But this issue was resolved fairly easily with this method.