where the map sensor is located if there was a leak at the intake gasket there would be less vacuum at the map sensor because the engine is sucking from anther spot not past the throttle plate. the map sensor would read a load on the engine and adjust accordingly. which would make it run rough, high idle, hunting. either way, every manifold leak no matter where will always effect the map reading because of its location directly behind the throttle plate before any gasket . if it was my car i would look for vacuum leaks first too. but a check engine light is always a valid question. it could help identify if there are other issuses. so what if a vacuum leak not even the problem or the whole problem? im simply trying to give him other things to look at/think about.