I've recently replaced the carb and had some performance enhancements done on the engine.
Now I'm only getting 6 to 8 mpg around town (12 on highway).with very reasonable driving style.
Is that normal or is something not dialed in right?

Here's the setup.
69 Firebird
400 CI engine, mostly stock except below.
Holley 4150 double pumper 750CFM carb
Butler Edelbrock D-Port, 72cc, Hyd. FT. Top End Package (intake, heads, mild cam)
https://butlerperformance.com/i-307...-ft-top-end-package-bpi-tep-dp-72ft.html
700r4 transmission and 3.73 differential.

The shop says everything is set up correctly but that 6 to 8mpg seems just incredibly low.

Any thoughts?