I own a 1992 nissan pickup 4x4 v6 and about a week ago it started using excessive amounts of gas. There is no leak present. It also runs and idles very rough. I have changed the 2 water temp sensors and the fuel pressure regulator. I took it to the shop spent 800.00 dollars on it and it still not fixed. Can u please give me some advise

Please help me get my 1992 nissan pickup where it wl not use excessive fuel. Changed 2 water temp sensors and fuel pressure regulator. Used 80 dollars in fuel in 30 miles