My 340 getting 6 mpg

Sheesh.. my 440 charger with 3:55's and 750DP holley 4 speed got 10 average. Definitely something wrong there that can be tweaked. Honestly, a bit of work but you could weld in an O2 sensor to leave in for readings while you're driving and see if the ratio changes during different behavior.

Outside of that, check for some gas leaks lol