a tad lean or a tad rich
Tech Resident
Joined: Jan 2006
Posts: 5,117
Likes: 3
From: Philly
Both.
Headers make you run rich down low, which is why people's mileage goes down when running untuned after a header install.
Headers make you run lean at WOT. It's not particularly good for the motor to go WOT without getting your A/F ratio tuned after a header install. Unlike a cam, you don't run the risk of quickly destroying your motor by not getting it tuned, but it can shorten the lifespan of your motor in the long run if you never get it tuned if you love to go WOT all the time.
Headers make you run rich down low, which is why people's mileage goes down when running untuned after a header install.
Headers make you run lean at WOT. It's not particularly good for the motor to go WOT without getting your A/F ratio tuned after a header install. Unlike a cam, you don't run the risk of quickly destroying your motor by not getting it tuned, but it can shorten the lifespan of your motor in the long run if you never get it tuned if you love to go WOT all the time.
