Originally Posted by oldford

Basic rules:
a) for optimum power you need 300 grams of fuel (petrol) for each Kilowatt the engine produces for an hour.
b) more absolute pressure in the inlet manifold is more power.
c) the further you depress the throttle, the higher the absolute pressure is in the manifold.

So, if you need 10 Kilowatt to drive a certain speed you need 3 kilograms of fuel per hour.
If you need 100 Kilowatt to drive a certain speed you need 30 kilograms of fuel per hour.

Back to your stage 1 chip: most chips I know will also use an increased ignition advance. That means you get (a little) more power from about the same amount of fuel. So, a stage 1 chip running at 10 psi could use a little less fuel then the standard chip with the same amount of boost. How much? You would have to try that.

As to overfueling the engine at low boost: if the chip is setup the right way, the answer is no. Remember, before you reach 15 psi, the pressure is 14 psi, and before that 13psi, etc. etc. You always run a small amount of time on 8 and 9 and 10 psi. If the fueling there is incorrect, the car will not accelerate very nicely.

Now, I wouldn't use a boost controller. I would let the chip control the boost pressure.
If you want high and low boost, all you have to do is put a switch in one of the electrical wires connected to the amal valve. I use a switch with a key, looks like an ignition barrel.