A LOT of variables, cannot simply build an air pan and expect great results. You will need more jetting for sure. If the scoop is sized properly for the application you will certainly see a gain. Those lexan boxes are NOT sized properly for much more than a grocery store 318.
How the scoop is configured inside matters too.
We fabbed a pan that went into the scoop - basically a Pro Stock style snorkel - to reduce the size of the opening and direct the air rather than just have it rolling around in there. Then used a pan on the carb to seal to that.
