i have the exact same problem on my 99 solara v6 se stick shift, P0441, and sometime P0446, i thought it was the gas cap, so i went to dealer and spent $23 for a new gas cap, it didn't fix the problem, it comes on about 50 to 100 miles after i reset the CEL,
so i bit the bullet and spent $200 on a brand new oem charcoal canister from dealer at bulter toyota online, took me more than an hour to replace the charcoal canister because there isn't much room to work with, it is located under the car, right behind the gas tank, between the two rears wheels. no need to remove anything else like exhaust or control arm, after you remove two 14mm bolts using a swing head ratchet it has enough room to slide out from the passenger sides.
i've driven with the new charcoal canister installed a good 500 miles, and no codes yet.
i read the problem was caused by topping the gas tank, which i did everytime to round off to the nearest dollar and squeezed more miles from single refill. the excess gas after the pump clicked vapors into to the charcoal canister, soaking and shorten the life of the charcoal canister.
now i never top off after the gas pump clicked.
i was thinking just changing the vsv and other purge valve, but i also heard if the charcoal canister is going bad, debris might clog the valve again later. and buy the whole charcoal canister assembly has all the valves included already, asides, separate valves are not cheap either.
Diamond Pearl White V6 SE 5 Speed Manual Transmission, Pure Black headlight with RS6 Bixenon HID projectors retrofit