I beleive it's due to less back pressure. I have seen my fuel consution
skyrocket from a open straight pipe.

Dan

<KnifeKnut@gmail.com> wrote in message
news:1108522596.679172.14270@f14g2000cwb.googlegro ups.com...
>
> vtecracing wrote:
> > Yes, a cracked exhaust manifold will result in excessive gas
> > consumption.
>
> Why?
>