I'm building a full header-back exhaust and need to trick my second O2 sensor into thinking the cat is still there so I don't throw codes.

I've found a trick that should work, but a few questions:

Do the 1NZ-FE engines use a narrow band rear O2 sensor?

If so, I should be able to solder a 1,000,000 ohm resistor and a 1 micro-farad capacitor across the signal and ground wires to raise the voltage seen by the ECU (as if the exhaust was still passing thru the cat)

 

would the antifouler trick not work for your car?

 

Resistors will not work. Antifouler/CEL eliminator will do the trick. Gen1 doesn't use wide band sensors.

 

So just moving the second O2 sensor out of the exhaust stream with a spark plug thread chaser should work? I've heard of this being used on the upstream sensor, but not the one after the Cat.

 

Never heard of it being used before the Cat. What for?

 

On the upstream sensor, to trick the motor into going rich for turbo/super applications.

I'm not going to use a spark-plug chaser, since I'm welding the whole thing I might as well just use some 3/4" black pipe and set the bung back a bit. Any idea on how far? Just enough to pull the tip of the O2 sensor out of the exhaust?

 

That's a real ghetto way to tune. Just going rich all across the range is not right but sure beats the price of anything else.
Google CEL eliminator images to get an idea. Sometimes you have to dial it in with the length so it's better not to make it a permanent setup.