A couple of years ago I witnessed Gen 3 Commodore do two dyno runs. 1. The first run was with a (two lettered) induction system fitted, and 2. The second was with the induction system removed (and no stock snorkel fitted) which gave a 10 rwkw increase. The guy operating the dyno said he show people with these induction systems that they restrict the amount of air into the engine. I removed the snorkel from my 2002 Corolla Levin, yesterday, and if feels less restricted and gives a nice note at wide open throttle. Once the snorkel is removed you an see how restricted it is. Give it a go! it cost nothing and the snorkel can be refitted if you want.