Will adding a fuel additive such as ca-40 or equivilant really help my fuel efficiency and save me gas noticeably?

No, not really. There is no magic bullet, or pill to improve mileage. Power comes from burning gas, without the combustion of fuel there is no heat to drive the motor. High performance is another way of saying higher temperature (power adders like boost and NOS just drive the temperature higher yet). A lower performing motor (your basic 350 Target Master with only 7.6:1 compression) is very inefficient due to low volumetric efficiency. In that it will burn nearly the same amount of gas as the high performance 350 but it wastes the energy, by pumping most of it out the exhaust due to cam timing and massive combustion chambers.

You can reduce the number of cubic inches with a 305, or go back to the six installed in most Nova's. The lower displacement burns less gas because all engines burn the exact same ratio of gas to air to initiate combustion (it is chemistry not determined by the engine design) and it is the displacement that determines the amount of air.

Big Dave

If you are looking for something to clean your entire system without all of the "HYPE", try this stuff....


http://www.bgfindashop.com/44K.htm

I have used this product in all 3 of my vehicles and had no fuel issues in 4 yrs. Use it 1 a year and it takes care of your entire system..