On 2000 Ford diesel they had a restriction device in the filler neck. Takes about 15 minutes to take out 3 screws and remove hose clamp. Once off I knocked out the restricter with hammer and screwdriver. Then replace unit back on vehicle. GMC apparently doesn't have that restricter. However, just a 15 min job for anyone that has that restricter.
They fit my 2013 just fine. I really like how quickly I can do a fill-up in the truck lanes, too!
U.S. Army retired 2020 Solitude 310GK-R MORryde IS, disc brakes, solar, DP windows (Previously in a Reflection 337RLS) 2012 F350 CC DRW Lariat 6.7 Full-time since 8/2015