i have a 1971 f-100 auto with 360 and 4 bbl on a two barrel intake i am planning on putting a four bbl intake on it but how good of gas millage whould i get if i put a two barrel back on now i drive about 3 miles and my gas gage drops a needle going that far whould you say it needs a tune up also

 

You will get better gas mileage with the 4 barrel.