Looking for help with P0441 (2001 V6)

I am looking for some help with my Tundra. It is a 2001 V6 Tundra with 137K miles (clam doors)

I live in Texas so my vehicle must pass inspection before I can renew the state vehicle registration. I have been trying to resolve a persistent P0441 (incorrect purge flow) for the last few months.

History:
Summer of 2017 (117K miles) I got a fault code for the CAT (this will be relevant at later). I was commuting between between cities for a new job and did not have time to deal with it myself. I had a friend that said he had a guy that could replace the CAT on the cheap. I had him do it. When I got the truck back I found that the muffler guy had cut and welded in a cheap aftermarket CAT. It is now one welded segment from the flange after the exhaust manifold pipe to the joint before the muffler. I was quite upset but there was nothing that could be done at this point.

During the summer of 2018 I replaced the timing belt myself and replaced the valve cover gaskets. I was very careful to label all hoses and connections during the process. Truck runs smooth.

The P0441 popped up in Oct/Nov. I noticed several of the vacuum lines were cracked. I replaced those, reset the codes and drove the truck. The code came back. I had a Firestone diagnose the issue. They ran a smoke test and found the vacuum canister to be leaking. I had a the canister replaced with a new Toyota canister. Reset the codes and drove the truck. The code P0441 came back as pending. I took it back to Firestone. They said they could find nothing wrong with the system. The only thing they noticed was a slight hiss at the gas cap when the gas tank was pressurized. They put the gas cap on the "gas cap tester" and it passed. The truck had a non-Toyota gas cap from the previous owner. They suggested putting on a Toyota gas cap. Since they could find nothing wrong with the truck they charged me $0. I purchased a toyota gas cap. I reset the codes and drove the truck. The P0441 came back as pending. It then went from Pending to a CEL. Then it went back to pending. I read the codes and I currently have a pending P0441 and a P0420 (catalyst system efficiency below Thrueshold). Several of the emissions stats still show up as incomplete so I still cannot get it inspected.

I took the truck to the dealer. They said the VSV was stuck open and needed to be replaced. As for the P420 they claimed that the CAT was bad and that the entire exhaust system had been compromised by the welded muffler work. Even though the new CAT has only 20k miles they claimed that it was already bad. They claimed that the compromised muffler system was the true source of all my issues. The dealer quoted me $4400 to replace the entire exhaust system. Due to the age of the truck and the cost of their suggested repairs they did not want to do any work on the truck. I pulled the VSV off yesterday and tested the VSV with clip leads on the battery. It works fine(no air flow when off and I can blow air freely through it when connected to the battery). I looked online and the two segments in the exhaust are about $2200 for OEM parts and about $400 for after market on RockAuto.

My life is a bit more stable than it was during the summer of 2017 so I now have the time to replace the exhaust myself if that is what is needed. However I dont really want to put the money into the exhaust until I know that the P0441 is fixable.

I have done various car repairs over the last 20 years. However I just dont have the tools and experience to diagnose the P0441. I am unsure what to do next. I like the Truck and would hate to dump it just because of a P0441.

 

Check the fuel filler neck.

The neck has the return line and the port where you stick the gas pump handle when you fill it up with gasoline. The return line is known to rust and get pin holes... throwing leak codes. The return line hose itself may also be crackin and brittle causing a leak. The hissing sound could also be where the return line hose hasn't been clamped hard enough which would explain the hiss.