It's a simple equation, more fuel=more performance, all things being
equal. There's no free lunch!
Depends on what you're after, and budget.
Then there's the factors of your right foot and conditions you drive in,
and the individual car you have, they are different.
Want 50+mpg?, drive like a little old lady and keep it stock, a basic
tune may improve efficiency.
Personally I've sacrificed FE for performance, I can give GTIs a run for
their money, for about half the fuel costs. What's not to like? {;o)