I would think you'd see an intake leak show up as much if not more at closed-throttle positions (cruising) due to higher engine vacuum, so I would look elsewhere. Personally, I'd be leaning toward the MAP (didn't know there was one in the Sonata), or I would clean the MAF. Still, if the MAF was faulty, you'd have starting/idle issues, which you don't have.
One final thought - if you have a bad vacuum line (split or crack) that opens under hard acceleration, that may be the culprit. You can check this by getting some spray throttle body cleaner and spraying around suspicious parts while the engine is idling (high vacuum). If there's a leak, the idle speed will change (up or down) depending on where it is and the volatility of the spray. We used to check manifold gasket leaks in old V-8's this way! (only then we used carb cleaner).
Good luck!