I'm kind of new here. Does adding a mod exhaust effect mpg?

 

Any intake or exhaust mods won't hurt gas mileage. Namely: axle-backs, cat-backs, cold air intakes, short ram intakes, mufflers, cat-delete pipes (but do this and you won't pass smog emissions tests).

(Turbos and superchargers can and do hurt gas mileage.)

 

Having an intake and exhaust may increase mileage in some cases. But don't always bet on it because most owners tend to have a heavier foot after adding i/h/e mods just cuz power (ie- speed in this case) is addicting...

 

I've always had the impression that the more air flow getting through the chamber would alter the timing and fuel management. But then again, I could be wrong.

 

JDMChris claims that his Jackson Racing/Rotrex supercharger maintains approx. the same gas mileage when driven lightly. That has me VERY interested in their upcoming kit.

Best mileage I've ever done so far with my A/T Sport - 267 miles to the half tank mark (H-Fit Supa Sucka Intake, J's Racing Header, Fujitsubo Power Getter Cat Back) mostly highway driving keeping it around 2500rpm's.