Loss of power, bad cats, no check engine lights, what is the root cause? Really? Help!

There is a problem with Tacomas, mine is a 2004 V6, 4x4 and I have seen people in other forums stating the same thing, maybe different years, but basically the same problems. Loss of power, no check engine light on ( or coming in), and some people have replaced everything including the engine. I myself had this start over a year ago, driving on freeway and it starts surging and losing power. Really bad. I take it in to a coupler repair shops. Same thing bad catalytic convertors. ok. yes it has about 267,000 miles on it, and cats can go bad, BUT I KNEW THEY USUALLY DONT, something makes them go bad(a bad influence, haha). However, since there are no more mechanics, just code readers now(sorry to the real car guys who know,repair and will diagnose the problems on cars/trucks), I just took it to the exhaust guy and bam, $1000 later I got knew cats and I am driving again, good as new. Six months later tops, I could feel it starting too surge and loss of power and now at 10 months, city streets only, no power, no check engine light.frigging joke. Ok checked and cleaned the MAS, it is OK. Took out and cleaned the front and back cat O2 sensors. Placed back into Taco and drove about 50 miles total to an appointment and no more lurching or surging, power wasn't back but it was better than before, check engine light was on. Dammit, after that appointment I had another and BAM, we are back too how it was before, lurching, no power, eating up gas like no tomorrow, oh and get this the check engine light goes away as soon as this crap started again.
Ok, I know my Cat is fried again or it could be a family of dead mongooses in my muffler, either way pricey exhaust $. I drove with the O2 sensors out, no lurching or surging and power was better, hella loud. I have read similar posts on forums about other poor bastards like myself and nobody has an answer. That is bullish#@! I bet toyota knows, or they should, which makes me think they know and aint telling cuz it will cost them. I have seen all sorts of suggestions or whatevers, but NEVER THE ROOT CAUSE OF this condition for the TACOS. I changes the plugs the boots and the wires. Bought my truck brand spanking new, and I love that truck, now its like it has rabies and Im going to have to pull an OLD YELLER on my trusted Taco.
So does anybody know what the hell is the root cause to mine or these problems. Please help.

Thanks, Gridster

 

No MIL on suggests to me fuel filter or fuel pump when was the last time the filter was changed?

What if any codes were pulled in the past ?

 

In most cases, the catalytic converter will last for the entire life cycle of a vehicle...but not always. While sturdy, the catalytic converter can slowly fail over time as the catalyst elements wear out. High mileage is not the only culprit, as failure could be due to an improperly operating engine.

Worn spark plugs, or burned and leaking exhaust valves, allow unburned fuel into the exhaust system, where it ignites in the catalytic converter and melts the internals. A weak ignition system can also cause the same problem, by not getting enough spark to the plugs.

Catalytic converter problems could also be something more serious, like heavily worn piston rings or jumped timing chain. These problems allow fuel or air into the wrong place at the wrong time. A head gasket or intake manifold leak can cause problems too, as oil or coolant can coat the catalyst, setting off a check engine light. On some older vehicles, a flashing check engine light will be your tipoff to catalytic converter overheating, and it shouldn't be ignored.

Keep in mind that the catalytic converter could fail again in a short time if an underlying issue is not fixed. Keep your ride tuned up, and your cat will live longer.

 

Read up on fuel trims and the function of an o2 sensor. Get a code reader and start poking around. Literally dozens of things it could be. Saying you're using a lot of fuel makes me think injectors. Rich mixture is a fast way to torch a cat.