Just picked up a 2001 with 79k miles and a few days after getting it home from the dealership the CEL came on (as well as VSC and TRAC lights). It has only a P0440 code, no accompanying codes at this point. I had the gas cap checked and it was good. Smoke tests revealed no leaks as well. I'd hate to spend $350 on a charcoal canister and have that not be the issue but not sure what else I can do at this point. Dealership denies having reset the codes before selling it so they won't take any responsibility or help with costs of the canister. I have no desire to have a Christmas tree of lights on the dash every time I drive though and resetting them only lasts for a week or so before they come back. Any ideas?

I didn't find any smoke leaking either when I ran a smoke test a few different times on my evap system. I found my P0440 leak by following the fsm steps for troubleshooting the evap system. My fix turned out to be the overfill check valve/gasket on top of the gas tank.

Unfortunately leaks can occur in a number of different spots throughout the evap system so there isn't a specific fix for that code. Since you have a 2001, this link might help, p0440 fix, it's a general summary of what I did to resolve the issue.

Thank you very much, I'm going to clean out my garage so I can bring it in and see if there's any fuel smells.

I was able to get the dealership I purchased it from to accept responsibility. They are replacing the gas tank check valve, charcoal canister and gas cap.

I was at another 4Runner forum for about 3 weeks maybe, but I had the dreaded P0440 code. My search engine is StartPage and I'm not sure what other words I used, but I did enter P0440 and just 3 results came back. I clicked the one for P0440 and read a whole lot.
I went down to where 45 replied with photos and fsm shots. The most important thing was that he listed all of the parts that were needed to fully rebuild the EVAP system. Thank you 45 for saving me a lot of time!
When the time comes to rebuild my EVAP system, I'll post some photos - you will not believe the shape of the underside is above the gas tank.
BTW this is the thread I an referring to
P0440 Fixed!

I fought p440 for 3 years. The plastic the overflow check valve on the fuel tank cracks around the top, the O ring for it cracks. You have to drop the tank to fix it. there are O-rings in some of the fittings I recommend taking a close look at and greasing. Check all the vacuum lines for the evap, change you vacuum lines under the hood. Get a new OEM fuel cap (this was my biggest problem).

Smoke machine will help, you can get them on amazon. Helped me find some of the vent lines were not completely seated (hence o-rings that need cleaning and grease to completely seat). I never saw any coming out of the gas cap until in was dark out, shined a flashlight DOWN and could see the shadow of fumes/smoke on the concrete. Swapping the cap from my wife's 5th gen completely solved the problem. Ended up getting her a new cap lol.