Gas Mileage Options

[o0black0o]

I put some 3-2-1 headers on bout 2 weeks ago. We also removed cat and placed a gutted one. I would of assumed i would be getting better gas mileage. but Im accually down 100 miles per tank. We did reset the ECU, via pulling the battery cable for 10 minutes. Shouldn't I get better mileage by at least like 1mpg or something or is this common? I have the 7afe so It might differ from the 5s.

Also I dono if this might be a cause but, I installed an auto meter A/F raito gauge its not reading. I currently have no Check Engine Light. But Since my light isn't on my O2 Sesor should be fine. Its only abour 3 months old. Am i right?

[Batman722]

getting less miles per tank is expected.

more flow = better performance
better performance = worse mileage

[Bitter]

getting less miles per tank is expected.

more flow = better performance
better performance = worse mileage

you'd think that, but the header actually works towards increasing VE by increasing scavenging which pulls more burnt gasses out and fresh charge in during valve overlap. the impact on fuel mileage should be negligible. i've noted NO change in my mileage despite a sharp jump in high rpm performance.