I have a 1997 Ultra Jet with a 502. It now has an 850 carb but it uses WAY too much fuel. What model can I go down to without losing a lot of power and performance? Holley.com says a 600 CFM. I went to the river and one trip about 30 miles I used 35 gallons of fuel. It costs me $120 for just one trip. Something must be wrong.. HELP!!!