I'm definitely following you. You're van is a few years older than my truck but we both live in FL (less rust issues) and it doesn't make sense to me that the CAT would become completely clogged overnight... I'll check the fuel pressure tomorrow and go from there. I think I'll pull the fuel tank tomorrow and inspect everything regardless. If nothing else, I can clean the tank, filters (or replace), and fuel line. Just to cover everything, have you ever had a problem with the fuel injectors not pulsing correctly causing similar symptoms? or water in the fuel?
Well I live in FL now for the past 5 years but my van spent about 10 years in NJ and well goes without saying.
As far as the fuel injectors go, no I haven't had an issue with the operating of the fuel injectors, I am a perfectionist the second I hear some kind of noise I drive home and have the van jacked up and I'm under it lol...
Generally if you have a fuel injector that is cycling properly then it would be because of generally 3 things, bad ECM (not likely), bad wire (possible with rodents), or a bad fuel injector (possible but again not likely). Check the resistance of a suspected injector, the resistance should be 14-15K ohms give or take. Do the ohm test quickly to avoid damage to the injector's solenoid coil. I generally use fuel injector or fuel injector + intake valve cleaner every 3000 Miles.
As for the fuel tank, you are likely to find some rust particles in the fuel tank and sometimes find the gas to be brown rust colour. Replacement of the fuel lines isn't needed, their are 3 filters on the pump and well that's plenty filter action. Just do a fuel pressure test and if it's low replace the whole pump, better off to replace the pump then try and salvage the old one. That web site that sells those pumps gives you a lifetime warranty, they will even pay shipping both ways.
As far as moisture in the tank it's going to happen. My van at one point sat for 4 years and I put a little gas it and it worked. If you have a moisture issue use of fuel injector cleaner generally eliminates any moisture in the fuel system.
Another thing to check in advance is the mounting bolts and nuts, sometimes they seiz and will need replacement. In my case I had to replace them (about 25 bucks) You will probably want to replace the filler neck tube grommet on the gas tank as well. The rubber dries out and cracks and can leak if reused. Grommet is only about 12 bucks cheap insurance for half tank of gas to go leaking.
I can tell you the best way to clean the tank from experience. Empty the tank as best as you can, then wash the outside of the tank with a garden hose and a rag. Then remove the pump, grommets, and the roll over valves if equipped. Then rinse the inside of the tank with water and empty and rise and then use your rag to clean the inside of the tank of any rust debris and then just rinse and since the tanks are black you can just put some shop towels in the tank then put that tank in the sun for 20 minutes and it will be bone dry. I for safety just wiped the inside of the tank dry with shop towels. I then put it all together used PTFE die electric lube on the rubber and grommets to help get them in then just put the tank back on the van put bottle of fuel injector cleaner and 5 gallons of fresh gas in and started it up. It only took about 3 hours, removing it was somewhat of a pain because of the frozen bolts but after that it was a piece of cake. Be sure to use locktite 242 (Blue) on the mounting hardware. Just need to tighten the straps snug.