who sifoo??...
because in highway, ur engine rpm is usually at mid to high range... at this range, engine sucks in alot of air.... by using open port, this reduces air restriction caused by oem airbox... besides, at high speed, cool air is rushed into engine bay due to momentum... thus, no need worry air filter sucking in hot air...
town drive usually at low to mid rpm... at low rpm, engine doesnt suck much air, thus airbox airflow restriction doesnt do much harm.... by using drop-in, u can utilise ur oem airbox CAI intake system.... thus, air filter doesnt suck hot air inside engine bay....