put in a vacum gauge, I did, and it's really helped me get more fuel economy. You don't even realize how much gas you waste when cruising until you "see" what you're doing wrong. A Vac gauge is easy to read, keep it at 10 PSI vacum or more to conserve. I used to think I could "feel" through the pedal how much the butterfly was open, man; I was WAAAY off. After driving with a vac gauge in the car, I realized how much gas I could save by being a bit lighter on the pedal.
Cruising, good Intakes
& exhaust will save you a little fuel, but when you jump on it, it'll suck fuel big time. So, both arguments are acvtually true.
When cruising, keeping an eye on the vac gauge, my mileage has improved somewhat, a full tank goes a lot further. Of course, if I jump on it and rev the motor hard, the fuel bars will start dropping a lot faster.
So, with gas being so pricey, I don't jump on my car much, maybe once or twice a week, this way, I usually spend about $10 on gas each week, and I drive a LOT!
Also remember to maintain your tire pressure, under inflation or over inflation can effect fuel economy.