Quote Originally Posted by Fivefingerdeathpunch View Post
Yes his car would run worse and get terrible gas mileage.

All 01+ cars use the rear o2 for diag and fueling of sorts in the PCM, if it has so cat all the readings will be wrong and thus dump fuel.

Isnt that what the rear O2 sim does, it simulates a working cat so the car diagnostics works... 97-00 dont need the sim just have an SES light till it gets tuned out. 01+ have Cat Diagnostics and NEED the O2 sim to go catless or else yes the computer dumps fuel.