So why is there a difference in clips between regular fuel and flex? I just did my 04 Yukon XL a few weekends ago. I didn't spend a whole lot of time before I just grabbed the saw and cut it off since I didn't have the tool. (Fire extinguisher nearby just in case.)
What I found was what appeared like a previous owner attempt. First off, it didn't appear like they used line wrenches due to some rounded edges on the fittings. It also appears like they never did get it off. Truck has under 80,000 miles on it and the fuel coming back out was black. Looked like old, runny, oil. When I looked at the connector on the end going towards the engine, they had screwed up the teeth in there something severe. They were all mangled. I ended up not even being able to get them to release the filter stub. I had to bust them out of there using some small allen wrenches to get in there to bend them out.
The new filter came with the plastic clip. It snapped in fine and I have not had a leak since. But now I read this post and am a little concerned. I am guessing that the flex fuel vehicles did not use the plastic clip because the E85 will eventually eat them? I don't really ever plan on running E85, but if this is the case, I better think about curing this issue before I forget!
(Sorry for the hijack!)