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No cat mileage

I redid my whole exhaust with a header, high flow cat and a terminator muffler with 2.5 an 3 inch pipe and I do get about 60 more miles per tank.
 
I put in a new high flow cat, glass pack, & tail-pipe and noticed about 1 mpg increase in gas mileage (I calculate my mileage with each fillup by dividing the miles driven by the gallons to fill it up).
 
Keep in mind that these numbers are probably with people ditching their old exhaust and old cats. It's like people who get a new carb and say it's so much better than their 22 year old original, un-rebuilt carb! :lecture: :laugh3:
 
There's no probably about it, we stated exactly what changes we'd made.
 
My cat is gone and it seemed to hurt my milage. My wife was driving it at the time though, so I couldn't tell you definitively how much.
 
I put a 2.5in cat & resonator on and have gained about 2 mpg. On a side note, I lost MPG when I staight piped my YJ.
 
I also ran just a header and down pipe for a couple weeks before putting the rest on, and it hurt my mileage and power quite a bit.
 
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