I have a very persistent P0441 check engine code on my '01 XJ 4.0 that I can't seem to get rid of, and thus won't be able to pass emissions. I have tried changing out lots of parts and lines that I thought it could be from reading on here and various other online resources. It just keeps coming back after i reset it. Here's what I've tried so far:

New purge valve solenoid
New mopar lines that go out of the purge valve solenoid
New mopar line that goes, i think, to the manifold from...i forget where it originates...leak detection pump?
New PCV valve and hoses and grommet
New breather tube and hoses and grommet
New mopar lines that run alongside the body to the vapor canister
New vapor canister
New mopar metal line that runs from the vapor canister to the gas tank (this connects to a plastic line, which i also inspected, and is fine. They don't make this line anymore)
Dropped the gas tank, inspected for any problems, none found that i could see, including on the hoses.
Relatively new mopar gas cap (this was done a few years ago, i am replacing this again this weekend just in case. probably should have tried this first though).
Relatively new leak detection pump (this was done a few years ago, I am thinking of replacing this again too).

Anyone have any other ideas of what could be the cause???? (i'm gonna laugh it's just the gas cap after all this work). I hear there might be a chance it's a bad computer? But that's unlikely? Or it could be a bad rollover valve in the gas tank, but can that even be tested for? I don't feel like replacing the whole gas tank on a "maybe".
I'm about to give up and either take it to the dealer or to a certified emissions technician...

I had the same code and the small vacuum line to the leak detection pump was plugged , the small plastic line was coming apart inside so just replaced it and all good . if that's not you problem it could be the computer to check it try to see if you can get it to give you a diffident evap code .

OK, I don't think I changed any leak detection pump lines yet, so I'll have to inspect those too, thanks for the input.
I should mention I was getting other emission codes too before I did all this work, like purge solenoid specific code. That seems to have gone away and the only code left is this p0441.

Now I "think" that was one of my codes I had on mine and I had to replace the line from gas tank to the canister and a rubber elbow. My line from tank had a pin hole.

Thanks for the service procedure too, I've seen that as well and have used it as a reference for trying n changing various things.

Yeah I changed the metal line that goes there, it was rusted. The plastic line n rubber connectors that connect to that line were in good shape when I inspected them, so I don't think that was the issue.

Yea I just saw that when I went to re-read it. I hate trying ti find evap issues...

Maybe I'll try a fog machine and do my own "smoke test" that way and see what happens. Might get lucky and find a leak.