If it is a stock car, which I am assuming it is, then there is no reason to be messing with the stock fuel maps. They are set to run a tad richer than stochiometric for safety reasons.

You don't want to run too lean or you will encounter detonation and you don't want to run too rich because it will waste gas and possibly foul the spark plugs.

I don't understand why you would want to do all this work for a stock car that has it's fuel maps set at an optimal point in terms of gas mileage and safety.