How many mpg will I gain from a dual Flowmaster 40 catback and a cheap cold air intake?

2002 Ford Mustang GT 4.6L v8|||You're not going to gain much as far as miles per gallon, but you'll add about 30-40 more horespower.|||Keep the smallest pipe size with that system you can get. You will need to do a tune on the computer to get everything right.|||I'll bet your mileage will get worse !! Bet you can't keep your foot out of the engine now, %26amp; that will be worse when you add the Flow Masters..... But, you didn't buy a V-8 for the mileage, anyway !!|||Nothing noticeable. Parts like that will not add mileage to a car. Modern cars do not have intake and exhaust systems restrictive enough to be affected in normal driving.|||ZERO.|||very little. probably won't even be noticable.|||You might pick up a mile per gallon and 15 horses.