Where I live there are no emissions requirements. I will have to replace a leaky exhaust manifold in the near future, would removing the cat converter and running straight pipes help my performance any. I have the 2.5 4 banger and every ounce of power gained would be a help. My thoughts are to…
Removing the cat will not affect gas mileage but removing the O2 sensor that is used for fuel control definitely will. There is an O2 sensor before (pre-) and after (post-) the cat. The pre-cat O2 sensor is used for feedback to control the amount of fuel needed. The post-cat O2 sensor is used to monitor the cat.
Running without catalytic converter? | Page 2 – Jeep Wrangler Forum
04 Sport with 3" Savvy Front Springs, 2" Rear BDS Springs, 1.25" BL, 1" MML, 33" Cooper STT’s, Currie TJJ Front Track Bar, RE Quick Discos, and other junk.
Measure the diameter of your exhaust pipe , then Hit a parts house and get a exhaust "turn down tip", bolt/clamp it on and head for the shop..[Let the exhaust shop know ahead of time what you have so they can order a Cat if they don”t have one in stock]