basic questions bout mods
 

can you all tell me what effect a cold air intake or exhaust system will have on gas mileage?

Air flow mods make your engine more efficient, giving you better gas mileage technically. If you floor it to hear the sound, etc. you'll be a little worse off. Gains/losses are marginal, so I really wouldn't worry about it when choosing whether to mod or not.

the exhaust and a cai won't give you too much of gains and won't affect your gas yardage too much, since you have the manifold as a bottle neck there.

you might get more fuel economy... except the fact you'll have the pedal to the metal playin with your newfound horsepower. which defeats the fuel savings. <shrug>