Exhaust high flowcatalytic converters with 02 housing.

On these cars the sensors go into a bung welded to the pipe before/after the cats. A high-flow cat of the correct pipe diameter is all you need. The existing bung(s) should work fine where they are.

Onlyoneromeo said:

Ok so there are two o2sensors right? One for each side ? And which do they go before or after the cat?

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There are four sensors, two on each side. The catalytic converter(s) lie between them. The upstream (front) sensors are used by the PCM to measure the exhaust gas before its chemical makeup is altered by the cats and this info is used to trim fuel delivery.

The downstream (rear) sensors are used by the PCM to check if the cats are operating properly.

You need to preserve the location of the four bungs when installing the cats on each bank.

Onlyoneromeo said:

Ok I just spoke to the previous owner and he said there were two sensors eliminated and then some special bungs put in to prevent the o2sensor from going all the way into the pipe. Anyone ever heard of this?

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The sensors are almost certain still there and not "eliminated." He may have been referring to the use of "MIL eliminators" which are electrical filters put between the sensor the PCM harness. It may also mean that the rear O2 sensor codes were disabled by the use of a tuner.

The use of a spacer on the rear O2 sensor is essentially an "analog" filter. The spacer creates a little cavity in the side of the pipe in which a bubble of exhaust gas circulates, being changed out more slowly than the main stream of exhaust passing by. This tends to present a more constant exhaust gas chemistry to the sensor to its output is "steadier" and thus has a better chance of being construed as normal to the PCM.