Quote Originally Posted by Fivefingerdeathpunch View Post
97-00 doesnt care about the rear o2 sensor for fueling. 01+ have the cat diag in the PCM that when the cat and rear o2 are removed will effect gas mileage.

On 01+ the cat can always be removed, but will require a tuner to shut off the diag and the code, the 97-00 will just need a tune to shut off the code and stop the SES from coming on.
The solution to this is just to remove the cat but not the two sensors so that the ECU will run the diagnostic process and it'll fail but the ECU will not report the code. Since the diagnostic sequence will run and then fail the ECU will not continue to run the diagnostic test which in turn will result in no excess fuel being used once said test is ran. Fuel is only wasted if that test is continued with no definitive result to be recorded as a pass or fail by the ECU. Like FFDP said the diagnostic procedure and cat codes will need to be turned off by someone with HPTuners.

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